Responsive Web Design - An Advanced Guide to HTML & CSS

The Internet took off quicker than anyone would have predicted, growing like crazy. Now, for the past few years, mobile growth has exploded onto the scene. The growth of mobile Internet usage is also far out pacing that of general Internet usage growth.

These days it is hard to find someone who doesn’t own a mobile device, or multiple, connected to the Internet. In the UK there are more mobile phones than people, and should trends continue mobile Internet usage will surpass that of desktop Internet usage within the year.

With the growth in mobile Internet usage comes the question of how to build websites suitable for all users. The industry response to this question has become responsive web design, also known as RWD.

Responsive Overview

Responsive web design is the practice of building a website suitable to work on every device and every screen size, no matter how large or small, mobile or desktop. Responsive web design is focused around providing an intuitive and gratifying experience for everyone. Desktop computer and cell phone users alike all benefit from responsive websites.

The responsive web design term itself was coined, and largely developed, by Ethan Marcotte. A lot of what is covered in this lesson was first talked about by Ethan online and in his book Responsive Web Design, which is worth a read.

Responsive vs. Adaptive vs. Mobile

For some the term responsive may not be new, and others might be even more acquainted with the terms adaptive or mobile. Which may leave you wondering what exactly is the difference between all of them.

Responsive and adaptive web design are closely related, and often transposed as one in the same. Responsive generally means to react quickly and positively to any change, while adaptive means to be easily modified for a new purpose or situation, such as change. With responsive design websites continually and fluidly change based on different factors, such as viewport width, while adaptive websites are built to a groups of preset factors. A combination of the two is ideal, providing the perfect formula for functional websites. Which term is used specifically doesn’t make a huge difference.

Mobile, on the other hand, generally means to build a separate website commonly on a new domain solely for mobile users. While this does occasionally have it’s place, it normally isn’t a great idea. Mobile websites can be extremely light but they do come with the dependencies of a new code base and browser sniffing, all of which can become an obstacle for both developers and users.

Currently the most popular technique lies within responsive web design, favoring design that dynamically adapts to different browser and device viewports, changing layout and content along the way. This solution has the benefits of being all three, responsive, adaptive, and mobile.

Flexible Layouts

Responsive web design is broken down into three main components, including flexible layouts, media queries, and flexible media. The first part, flexible layouts, is the practice of building the layout of a website with a flexible grid, capable of dynamically resizing to any width. Flexible grids are built using relative length units, most commonly percentages or em units. These relative lengths are then used to declare common grid property values such as width, margin, or padding.

Flexible layouts do not advocate the use of fixed measurement units, such as pixels or inches. Reason being, the viewport height and width continually change from device to device. Website layouts need to adapt to this change and fixed values have too many constraints. Fortunately, Ethan pointed out an easy formula to help identify the proportions of a flexible layout using relative values.

The formula is based around taking the target width of an element and dividing it by the width of it’s parent element. The result is the relative width of the target element.

target ÷ context = result

Flexible Grid

Let’s see how this formula works inside of a two column layout. Below we have a parent division with the class of container wrapping both the section and aside elements. The goal is to have have the section on the left and the aside on the right, with equal margins between the two. Normally the markup and styles for this layout would look a bit like the following.

<div class="container"><section>...</section><aside>...</aside></div>

.container {
 width: 660px;
}
section {
 float: left;
 margin: 10px;
 width: 420px;
}
aside {
 float: right;
 margin: 10px;
 width: 200px;
}

Using the flexible grid formula we can take all of the fixed units of length and turn them into relative units. In this example we’ll use percentages but em units would work equally as well. Notice, no matter how wide the parent container becomes, the section and aside margins and widths scale proportionally.

.container {
 max-width: 660px;
}
section {
 float: left;
 margin: 1.51515151%; /* 10px ÷ 660px = .01515151 */
 width: 63.63636363%; /* 420px ÷ 660px = .63636363 */ 
}
aside {
 float: right;
 margin: 1.51515151%; /* 10px ÷ 660px = .01515151 */
 width: 30.30303030%; /* 200px ÷ 660px = .30303030 */
}

Taking the flexible layout concept, and formula, and reapplying it to all parts of a grid will create a completely dynamic website, scaling to every viewport size. For even more control within a flexible layout, you can also leverage the min-width, max-width, min-height, and max-height properties, as done with the parent container above.

The flexible layout approach alone isn’t enough. At times the width of a browser viewport may be so small that even scaling the the layout proportionally will create columns that are too small to effectively display content. Specifically, when the layout gets too small, or too large, text may become illegible and the layout may begin to break. In this event, media queries can be used to help build a better experience.

Media queries were built as an extension to media types commonly found when targeting and including styles. Media queries provide the ability to specify different styles for individual browser and device circumstances, the width of the viewport or device orientation for example. Being able to apply uniquely targeted styles opens up a world of opportunity and leverage to responsive web design.

Initializing Media Queries

There are a couple different ways to use media queries, using the @media rule inside of an existing style sheet, importing a new style sheet using the @import rule, or by linking to a separate style sheet from within the HTML document. Generally speaking it is recommend to use the @media rule inside of an existing style sheet to avoid any additional HTTP requests.

<!-- Separate CSS File --><link href="styles.css" rel="stylesheet" 
media="all and (max-width: 1024px)">

/* @media Rule */
@media all and (max-width: 1024px) {...}
/* @import Rule */
@import url(styles.css) all and (max-width: 1024px) {...}

Each media query may include a media type followed by one or more expressions. Common media types include all, screen, print, tv, and braille. The HTML5 specification includes new media types, even including 3d-glasses. Should a media type not be specified the media query will default the media type to screen.

The media query expression that follows the media type may include different media features and values, which then allocate to be true or false. When a media feature and value allocate to true, the styles are applied. If the media feature and value allocate to false the styles are ignored.

Logical Operators in Media Queries

Logical operators in media queries help build powerful expressions. There are three different logical operators available for use within media queries, including and, not, and only.

Using the and logical operator within a media query allows an extra condition to be added, making sure that a browser or devices does both a, b, c, and so forth. Multiple individual media queries can be comma separated, acting as an unspoken or operator. The example below selects all media types between 800 and 1024 pixels wide.

@media all and (min-width: 800px) and (max-width: 1024px) {...}

The not logical operator negates the query, specifying any query but the one identified. In the example below the expression applies to any device that does not have a color screen. Black and white or monochrome screens would apply here for example.

@media not screen and (color) {...}

The only logical operator is a new operator and is not recognized by user agents using the HTML4 algorithm, thus hiding the styles from devices or browsers that don’t support media queries. Below, the expression selects only screens in a portrait orientation that have a user agent capable of rending media queries.

@media only screen and (orientation: portrait) {...}

Media Features in Media Queries

Knowing the media query syntax and how logical operators work is a great introduction to media queries but the true work comes with media features. Media features identify what attributes or properties will be targeted within the media query expression.

Height & Width Media Features

One of the most common media features revolves around determining a height or width for a device or browser viewport. The height and width may be found by using the height, width, device-height, and device-width media features. Each of these media features may then also be prefixed with the min or max qualifiers, building a feature such as min-width or max-device-width.

The height and width features are based off the height and width of the viewport rendering area, the browser window for example. The device-height and device-width features, on the other hand, are based off the height and width of the output device, which may be larger than the actual rendering area. Values for these height and width media features may be any length unit, relative or absolute.

Height & Width@media all and (min-width: 320px) and (max-width: 780px) {...}

Within responsive design the most commonly used features include min-width and max-width. These help build responsive websites on desktops and mobile devices equally, avoiding any confusion with device features.

Orientation Media Feature

The orientation media feature determines if a device is in the landscape or portrait orientation. The landscape mode is triggered when the display is wider than taller and the portrait mode is triggered when the display is taller than wider. This media feature plays a part largely with mobile devices.

@media all and (orientation: landscape) {...}

Aspect Ratio Media Features

The aspect-ratio and device-aspect-ratio features specifies the width/height pixel ratio of the targeted rendering area or output device. The min and max prefixes are available to use with the different aspect ratio features, identifying a ratio above or below that of which is stated.

The value for the aspect ratio feature consist of two positive integers separated by a forward slash. The first integer identifies the width in pixels while the second integer identifies the height in pixels.

@media all and (min-device-pixel-ratio: 16/9) {...}

@media only screen and (-webkit-min-device-pixel-ratio: 1.3), 
 only screen and (min-device-pixel-ratio: 1.3) {...}

Resolution Media Feature

The resolution media feature specifies the resolution of the output device in pixel density, also known as dots per inch or DPI. The resolution media feature does accept the min and max prefixes. Additionally, the resolution media feature will accept dots per pixel (1.3dppx), dots per centimeter (118dpcm), and other length based resolution values.

@media print and (min-resolution: 300dpi) {...}

Other Media Features

Other media features include identifying available output colors with use of the color, color-index, and monochrome features, identifying bitmap devices with the grid feature, and identifying the scanning process of a television with the scan feature. These features are less common but equally as helpful when needed.

Media Queries Demo

Using media queries we will now rewrite the flexible layout we built previously. One of the current problems within the demo appears when the aside width becomes uselessly small within smaller viewports. Adding a media query for viewports under 420 pixels wide we can change the layout by turning off the floats and changing the widths of the section and aside.

@media all and (max-width: 420px) {
 section, aside {
 float: none;
 width: auto;
 }
}

Mobile First

One popular technique with using media queries is called mobile first. The mobile first approach includes using styles targeted at smaller viewports as the default styles for a website, then use media queries to add styles as the viewport grows.

The operating belief behind mobile first design is that a user on a mobile device, commonly using a smaller viewport, should’t have to load the styles for a desktop computer only to have them over written with mobile styles later. Doing so is a waste of bandwidth. Bandwidth that is precious to any users looking for a snappy website.

The mobile first approach also advocates designing with the constraints of a mobile user in mind. Before too long, the majority of Internet consumption will be done on a mobile device. Plan for them accordingly and develop intrinsic mobile experiences.

A breakout of mobile first media queries might look at bit like the following.

/* Default styles first then media queries */
@media screen and (min-width: 400px) {...}
@media screen and (min-width: 600px) {...}
@media screen and (min-width: 1000px) {...}
@media screen and (min-width: 1400px) {...}

Additionally, downloading unnecessary media assets can be stopped by using media queries. Generally speaking, avoiding CSS3 shadows, gradients, transforms, and animations within mobile styles isn’t a bad idea either. When used excessively, they cause heavy loading and can even reduce a device’s battery life.

/* Default media */
body {
 background: #ddd;
}
/* Media for larger devices */
@media screen and (min-width: 800px) {
 body {
 background-image: url("bg.png") 50% 50% no-repeat;
 }
}

Mobile First Demo

Adding media queries to our previous example, we overwrote a handful of styles in order to have a better layout on viewports under 420 pixels wide. Rewriting this code to use the mobile styles first by default then adding media queries to adjust for viewports over 420 pixels wide we build the following:

View this code in action.

section, aside {
 margin: 1.51515151%;
}
@media all and (min-width: 420px) {
 .container {
 max-width: 660px;
 }
 section {
 float: left;
 width: 63.63636363%;
 }
 aside {
 float: right;
 width: 30.30303030%;
 }
}

Notice, this is the same amount of code as before. The only exception here is that mobile devices only have to render only one CSS declaration. All of the other styles are deferred, only loading on larger viewports and done so without overwriting any initial styles.

Viewport

Mobile devices generally do a pretty decent job of displaying websites these days. Sometimes they could use a little assistance though, particularly around identifying the viewport size, scale, and resolution of a website. To remedy this, Apple invented the viewport meta tag.

Viewport Height & Width

Using the viewport meta tag with either the height or width values will define the height or width of the viewport respectively. Each value accepts either a positive integer or keyword. For the height property the keyword device-height value is accepted, and for the width property the keyword device-width is accepted. Using these keywords will inherit the device’s default height and width value.

For the best results, and the best looking website, it is recommend that you use the device defaults by applying the device-height and device-width values.

Height & Width<meta name="viewport" content="width=device-width">

Viewport Scale

To control how a website is scaled on a mobile device, and how users can continue to scale a website, use the minimum-scale, maximum-scale, initial-scale, and user-scalable properties.

The initial-scale of a website should be set to 1 as this defines the ratio between the device height, while in a portrait orientation, and the viewport size. Should a device be in landscape mode this would be the ratio between the device width and the viewport size. Values for initial-scale should always be a positive integer between 0 and 10.

<meta name="viewport" content="initial-scale=2">

The minimum-scale and maximum-scale values determine how small and how large a viewport may be scaled. When using minimum-scale the value should be a positive integer lower than or equal to the initial-scale. Using the same reasoning, the maximum-scale value should be a positive integer greater than or equal to the initial-scale. Values for both of these must also be between 0 and 10.

Minimum & Maximum Scale<meta name="viewport" content="minimum-scale=0">

Generally speaking, these values should not be set to the same value as the initial-scale. This would disable any zooming, which can be accomplished instead by using the user-scalable value. Setting the user-scalable value to no will disable any zooming. Alternatively, setting the user-scalable value to yes will turn on zooming.

Turning off the ability to scale a website is a bad idea. It harms accessibility and usability, preventing those with disabilities from viewing a website as desired.

<meta name="viewport" content="user-scalable=yes">

Viewport Resolution

Letting the browser decide how to scale a website based off any viewport scale values usually does the trick. When more control is needed, specifically over the resolution of a device, the target-densitydpi value may be used. The target-densitydpi viewport accepts a handful of values including device-dpi, high-dpi, medium-dpi, low-dpi, or an actual DPI number.

Using the target-densitydpi viewport value is rare, but extremely helpful when pixel by pixel control is needed.

<meta name="viewport" content="target-densitydpi=device-dpi">

Combining Viewport Values

The viewport meta tag will accept individual values as well as multiple values, allowing multiple viewport properties to be set at once. Setting multiple values requires comma separating them within the content attribute value. One of the recommended viewport values is outlined below, using both the width and initial-scale properties.

<meta name="viewport" content="width=device-width, initial-scale=1">

@viewport {
 width: device-width;
 zoom: 1;
}

The final, equally important aspect to responsive web design involves flexible media. As viewports begin to change size media doesn’t always follow suit. Images, videos, and other media types need to be scalable, changing their size as the size of the viewport changes.

One quick way to make media scalable is by using the max-width property with a value of 100%. Doing so ensures that as the viewport gets smaller any media will scale down according to its containers width.

img, video, canvas {
 max-width: 100%;
}

Flexible Embedded Media

Unfortunately the max-width property doesn’t work well for all instances of media, specifically around iframes and embedded media. When it comes to third party websites, such as YouTube, who use iframes for embedded media this is a huge disappointment. Fortunately, there is a work around.

To get embedded media to be fully responsive, the embedded element needs to be absolutely positioned within a parent element. The parent element needs to have a width of 100% so that it may scale based on the width of the viewport. The parent element also needs to have a height of 0 to trigger the hasLayout mechanism within Internet Explorer.

Padding is then given to the bottom of the parent element, the value of which is set in the same aspect ratio of the video. This allows the height of the parent element to be proportionate to that of it’s width. Remember the responsive design formula from before? If a video has an aspect ratio of 16:9, 9 divided by 16 equals .5625, thus requiring a bottom padding of 56.25%. Padding on the bottom and not the top is specifically used to prevent Internet Explorer 5.5 from breaking, and treating the parent element as an absolutely positioned element.

<figure><iframe src="https://www.youtube.com/embed/4Fqg43ozz7A"></iframe></figure>

figure {
 height: 0;
 padding-top: 56.25%; /* 16:9 */
 position: relative;
 width: 100%;
}
iframe {
 height: 100%;
 left: 0;
 position: absolute;
 top: 0;
 width: 100%;
}

Resources & Links

Complete! Any questions?

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