Welcome to the world of the Responsive Web Design! This article is written by Dejan Markovic, author of the book WordPress Responsive Theme Design, and it will introduce you to the Responsive Web Design and its concepts and techniques. It will also present crisp notes from WordPress Responsive Theme Design.

(For more resources related to this topic, see here.)

Responsive web design (RWD) is a web design approach aimed at crafting sites to provide an optimal viewing experience—easy reading and navigation with a minimum of resizing, panning, and scrolling—across a wide range of devices (from mobile phones to desktop computer monitors).

Reference: http://en.wikipedia.org/wiki/Responsive_web_design.

To say it simply, responsive web design (RWD) means that the responsive website should adapt to the screen size of the device it is being viewed on.

When I began my web development journey in 2002, we didn't have to consider as many factors as we do today.

We just had to create the website for a 17-inch screen (which was the standard at that time), and that was it. Yes, we also had to consider 15, 19, and 21-inch monitors, but since the 17-inch screen was the standard, that was the target screen size for us. In pixels, these sizes were usually 800 or 1024. We also had to consider a fewer number of browsers (Internet Explorer, Netscape, and Opera) and the styling for the print, and that was it.

Since then, a lot of things have changed, and today, in 2015, for a website design, we have to consider multiple factors, such as:

• A lot of different web browsers (Internet Explorer, Firefox, Opera, Chrome, and Safari)
• A number of different operating systems (Windows (XP, 7, and 8), Mac OS X, Linux, Unix, iOS, Android, and Windows phones)
• Device screen sizes (desktop, mobile, and tablet)
• Is content accessible and readable with screen readers?
• How the content will look like when it's printed?

Today, creating different design for all these listed factors & devices would take years. This is where a responsive web design comes to the rescue.

The concepts of RWD

I have to point out that the mobile environment is becoming more important factor than the desktop environment. Mobile browsing is becoming bigger than the desktop-based access, which makes the mobile environment very important factor to consider when developing a website. Simply put, the main point of RWD is that the layout changes based on the size and capabilities of the device its being viewed on. The concepts of RWD, that we will learn next, are: Viewport, scaling and screen density.

Controlling Viewport

On the desktop, Viewport is the screen size of the window in a browser. For example, when we resize the browser window, we are actually changing the Viewport size.

On mobile devices, the Viewport size is also independent of the device screen size. For example, Viewport is 850 px for mobile Opera and 980 px for mobile Safari, and the screen size for iPhone is 320 px.

If we compare the Viewport size of 980 px and the screen size of an iPhone of 320 px, we can see that Viewport is bigger than the screen size. This is because mobile browsers function differently. They first load the page into Viewport, and then they resize it to the device's screen size. This is why we are able to see the whole page on the mobile device.

If the mobile browsers had Viewport the same as the screen size (320 px), we would be able to see only a part of the page on the mobile device.

In the following screenshot, we can see the table with the list of Viewport sizes for some iPhone models:



We can control Viewport with CSS:

@viewport {width: device-width;}

Or, we can control it with the meta tag:

<meta name="viewport" content="width=device-width">

In the preceding code, we are matching the Viewport width with the device width.

Because the Viewport meta tag approach is more widely adopted, as it was first used on iOS and the @viewport approach was not supported by some browsers, we will use the meta tag approach.

We are setting the Viewport width in order to match our web content with our mobile content, as we want to make sure that our web content looks good on a mobile device as well.

We can set Viewports in the code for each device separately, for example, 320 px for the iPhone. The better approach will be to use content="width=device-width".

Scaling

Scaling is extremely important, as the initial scale controls the zoom aspect of the content for the initial look of the page. For example, if the initial scale is set to 3, the content will be loaded in the size of 3 times of the Viewport size, which means 3 times zoom. Here is the look of the screenshot for initial-scale=1 and initial-scale=3:



As we can see from the preceding screenshots, on the initial scale 3 (three times zoom), the logo image takes the bigger part of the screen.

It is important to note that this is just the initial scale, which means that the user can zoom in and zoom out later, if they want to.

Here is the example of the code with the initial scale:

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

In this example, we have used the maximum-scale=1 option, which means that the user will not be able to use the zoom here. We should avoid using the maximum-scale property because of accessibility issues. If we forbid zooming on our pages, users with visual problems will not be able to see the content properly.

The screen density

As the screen technology is going forward every year or even faster than that, we have to consider the screen density aspect as well. Screen density is the number of pixels that are contained within a screen area. This means that if the screen density is higher, we can have more details, in this case, pixels in the same area.

There are two measurements that are usually used for this, dots per inch (DPI) and pixels per inch (PPI). DPI means how many drops a printer can place in an inch of a space. PPI is the number of pixels we can have in one inch of the screen. If we go back to the preceding screenshot with the table where we are showing Viewports and densities and compare the values of iPhone 3G and iPhone 4S, we will see that the screen size stayed the same at 3.5 inch, Viewport stayed the same at 320 px, but the screen density has doubled, from 163 dpi to 326 dpi, which means that the screen resolution also has doubled from 320x480 to 640x960. The screen density is very relevant to RWD, as newer devices have bigger densities and we should do our best to cover as many densities as we can in order to provide a better experience for end users.

Pixels' density matters more than the resolution or screen size, because more pixels is equal to sharper display:



There are topics that need to be taken into consideration, such as hardware, reference pixels, and the device-pixel-ratio, too.

Problems and solutions with the screen density

Scalable vector graphics and CSS graphics will scale to the resolution.

This is why I recommend using Font Awesome icons in your project. Font Awesome icons are available for download at: http://fortawesome.github.io/Font-Awesome/icons/.

Font Icons is a font that is made up of symbols, icons, or pictograms (whatever you prefer to call them) that you can use in a webpage just like a font. They can be instantly customized with properties like: size, drop shadow, or anything you want can be done with the power of CSS.

The real problem triggered by the change in the screen density is images, as for high-density screens, we should provide higher resolution images.

There are several ways through which we can approach this problem:

• By targeting high-density screens (providing high-resolution images to all screens)
• By providing high-resolution images where appropriate (loading high-resolution images only on devices with high-resolution screens)
• By not using high-resolution images

For the beginner developers I will recommend using second approach, providing high-resolution images where appropriate.

Techniques in RWD

RWD consists of three coding techniques:

• Media queries (adapt content to specific screen sizes)
• Fluid grids (for flexible layouts)
• Flexible images and media (that respond to changes to screen sizes)

More detailed information about RWD techniques by Ethan Marcote, who coined the term Reponsive Web Design, is available at http://alistapart.com/article/responsive-web-design.

Media queries

Media queries are CSS modules, or as some people like to say, just a conditional statements, which are telling tells the browsers to use a specific type of style, depending on the size of the screen and other factors, such as print (specific styles for print). They are here for a long time already, as I was using different styles for print in 2002.

If you wish to know more about media queries, refer to W3C Candidate Recommendation 8 July 2002 at http://www.w3.org/TR/2002/CR-css3-mediaqueries-20020708/.

Here is an example of media query declaration:

@media only screen and (min-width:500px) {
font-family: sans-serif;
}

Let's explain the preceding code:

The @media code means that it is a media type declaration.

The screen and part of the query is an expression or condition (in this case, it means only screen and no print).

The following conditional statement means that everything above 500 px will have the font family of sans serif:

(min-width:500px) {
font-family: sans-serif;
}

Here is another example of a media query declaration:

@media only screen and (min-width: 500px), screen and (orientation: portrait) {
font-family: sans-serif;
}

In this case, if we have two statements and if one of the statements is true, the entire declaration is applied (either everything above 50 px or the portrait orientation will be applied to the screen).

The only keyword hides the styles from older browsers.

As some older browsers don't support media queries, I recommend using a respond.js script, which will "patch" support for them.

Polyfill (or polyfiller) is code that provides features that are not built or supported by some web browsers. For example, a number of HTML5 features are not supported by older versions of IE (older than 8 or 9), but these features can be used if polyfill is installed on the web page. This means that if the developer wants to use these features, he/she can just include that polyfill library and these features will work in older browsers.

Breakpoints

Breakpoint is a moment when layout switches, from one layout to another, when some condition is fulfilled, for example, the screen has been resized. Almost all responsive designs cover the changes of the screen between the desktop, tablets, and smart phones.

Here is an example with comments inside:

@media only screen and (max-width: 480px) {
//mobile styles
// up to 480px size
}

Media query in the preceding code will only be used if the width of the screen is 480 px or less.

@media only screen and (min-width:481px) and (max-width: 768px) {
//tablet styles
//between 481 and 768px
}

Media query in the preceding code will only be used if the width of the screen is between the 481 px and 768 px.

@media only screen and (min-width:769px) {
//desktop styles
//from 769px and up
}

Media query in the preceding code will only be used when the width of the screen is 769 px and more.

The minimum width value in desktop styles is 1 pixel over the maximum width value in tablet styles, and the same difference is there between values from tablet and mobile styles. We are doing this in order to avoid overlapping, as that could cause problem with our styles.

There is also an approach to set the maximum width and minimum width with em values. Setting em of the screen for maximum will mean that the width of the screen is set relative to the device's font size. If the font size for the device is 16 px (which is the usual size), the maximum width for mobile styles would be 480/16=30. Why do we use em values? With pixel sizes, everything is fixed; for example, h1 is 19 px (or 1.5 em of the default size of 16 px), and that's it. With em sizes, everything is relative, so if we change the default value in the browser from, for example, 16 px to 18 px, everything relative to that will change.

Therefore, all h1 values will change from 19 px to 22 px and make our layout "zoomable". Here is the example with sizes changed to em:

@media only screen and (max-width: 30em) {
//mobile styles
// up to 480px size
}
 
@media only screen and (min-width:30em) and (max-width: 48em) {
//tablet styles
//between 481 and 768px
}
 
@media only screen and (min-width:48em) {
//desktop styles
//from 769px and up
}

Fluid grids

The major point in RWD is that the content should adapt to any screen it's viewed on. One of the best solutions to do this is to use fluid layouts where our content can be resized on each breakpoint.

In fluid grids, we define a maximum layout size for the design. The grid is divided into a specific number of columns to keep the layout clean and easy to handle. Then we design each element with proportional widths and heights instead of pixel based dimensions. So whenever the device or screen size is changed, elements will adjust their widths and heights by the specified proportions to its parent container.

Reference: http://www.1stwebdesigner.com/tutorials/fluid-grids-in-responsive-design/.

To make the grid flexible (or elastic), we can use the % points, or we can use the em values, whichever suits us better. We can make our own fluid grids, or we can use grid frameworks. As there are so many frameworks available, I would recommend that you use the existing framework rather than building your own.

Grid frameworks could use a single grid that covers various screen sizes, or we can have multiple grids for each of the break points or screen size categories, such as mobiles, tablets, and desktops.

Some of the notable frameworks are Twitter's Bootstrap, Foundation, and SemanticUI. I prefer Twitter's Bootstrap, as it really helps me speed up the process and it is the most used framework currently.

Flexible images and media

Last but not the least important, are images and media (videos). The problem with them is that they are elements that come with fixed sizes. There are several approaches to fix this:

• Replacing dimensions with percentage values
• Using maximum widths
• Using background images only for some cases, as these are not good for accessibility
• Using some libraries, such as Scott Jehl's picturefill (https://github.com/scottjehl/picturefill)
• Taking out the width and height parameters from the image tag and dealing with dimensions in CSS

Summary

In this article, you learned about the RWD concepts such as: Viewport, scaling and the screen density. Also, we have covered the RWD techniques: media queries, fluid grids, and flexible media.

Resources for Article:

• Deployment Preparations [article]
• Why Meteor Rocks! [article]
• Clustering and Other Unsupervised Learning Methods [article]