In the past, I haven’t done a lot of CSS work; my interests lie more in the areas of SEO and content. We needed a WordPress programmer, though, and before I could start programming WordPress themes, I needed to brush up on my CSS and PHP. Fortunately, I had a decent book sitting around: O’Reilly’s CSS: The Missing Manual. After a few hours reading the book and playing with the CSS in some WordPress themes, it all makes sense; my only hesitation in recommending the book comes from the fact that, because it was released last year, it contains less than a hundred pages on CSS3.
I’ve probably mentioned this before, but if you’re not familiar with what Cascading Style Sheets can do, you need to run, not walk, over to the css Zen Garden and play with it a bit. Good programming practice for the web these days, and what HTML5 is built on, is the separation of style from content. HTML5 holds the content; CSS should be used to indicate to the browser how to display it. What’s really nice about this is that by using an external style sheet for your website, if you decide to change the look and feel of the site you can immediately alter every page (drastically, if desired) simply by editing one file.
CSS is really pretty simple. Suppose that I wanted to change how the text in each of these posts is displayed. Let’s say that, for some reason, I wanted the text to appear in bright orange. In WordPress, the posts are contained in the following tags: <div id=”content”></div>. Thus, I would simply add the following code to my style.css file:
background: #FFFFFF url(‘images/background.jpg’) no-repeat;
So what does all that mean? The hash mark before the name of the div means that this is an ID, which is something that should appear at most once on each page; something that can appear multiple times should be a class and is indicated using a period. Everything between the brackets is CSS code that will apply to the contents of the content div; in this case, #content is called a selector because it selects this particular part of the HTML. Inside the brackets I can have any number of declarations; in this case I just have two. Each declaration is a property followed by a colon and then a value; some properties can take on multiple values. For example, here I told the browser that it should render the content area with a white background, use the file background.jpg in the images directory as a background image, and that that image should not repeat. If I later decide to use a less hideous color combination, all I have to do is edit this one file.
Aside from making my life a lot easier when I have to change something, this can also reduce the amount of space the code for a site takes up, as the formatting only has to be stored (and downloaded) once, rather than once for each page. This helps speed up the process of loading your site, which helps to keep Google and your customers happy.