Reset your CSS

All browsers have default styles applied to certain HTML elements. For example, a h1 element is bold and larger by default, and has some margin too. The problem is that all browsers have different default styles so your h1 won’t look the same in every browser. The font-size isn’t really

The solution is to reset the default styles of each browser and build it up again with your own styles. Because you’ve removed the standard browser styles, there won’t be any difference between the browsers. It’s like starting on a clean sheet.

There are a lot of CSS Resets available but Eric Meyer’s CSS Reset is the most popular, according to a poll on CSS-Tricks. A round up of the most used CSS Resets can be found on here.

The disadvantage of a CSS reset is that you have to write a lot more code. Every element you reset, has to be build up again. That’s the reason why a lot of designers use a custom CSS Reset (13% according to the CSS-Tricks poll) or no CSS reset at all. Veerle Pieters showed her limited CSS Reset in a reply to a question of mine.

A CSS Reset is important for cross browser compatibility, but you have to decide for yourself how far you must go when resetting your CSS file.

Using supported techniques

CSS offers a lot of techniques, but not all of them are good supported by every browser. For example the :before and :after pseudo selectors, which don’t work in any version of Internet Explorer, shouldn’t be used.

Nor should the attribute selectors (like a[href $='.pdf']), for their bad browser support. If you want to use the attribute selectors, use jQuery instead of CSS. jQuery is a good way to imitate CSS selectors. It can be downloaded here.

A good overview of CSS Selectors and their browser support can be found here.

Validate

I think this one is obvious: Take the time to validate your CSS styles. Cross browser compatibility is way easier with good and valid CSS. You can validate your CSS file using the W3 CSS Validator.

Summary

Follow these three guidelines and your CSS file will have a lot more browser support:

• Reset your CSS,
• Use only supported techniques and…
• Validate!

What are the techniques that you use to assure cross browser compatibility? Please leave a comment and share your thoughts.

Further Reading

• Make your site cross browser compatible in 5 steps
• CSS hacks inside CSS

Step 1: Validate

Lots of bugs are caused by invalid (X)HTML or CSS. If you have your site validated, it will be a lot easier to make it cross browser compatible. Validate your (X)HTML code with the W3C validator and your CSS file with the W3C CSS validator.

Step 2: Check your Website

Now you have to check your website in all browsers. I always check my site in the browsers, I’ve installed on my computer (Opera, Safari, Internet Explorer and Firefox). Do it and make a note of the bugs.

Of course, checking your website in the browsers installed on your computer is not enough. You have to check the website in different browser versions on different operating systems. The solution is Browsershots.org. With this website you can take full-length screen shots of your website in a lot of browsers. Just type in your url, bookmark the page and come back 20 minutes later to view the screen shots.

Analyse the screen shots and look for bugs. Be sure to write them down.

Step 3: Is it worth my time?

If you notice bugs in very old or uncommon used browsers, ask yourself if it’s worth your time to fix the problems. Look at the browser statistics of w3schools.com, but don’t forget to look to your own stats (I recommend AWstats). If you have one or two visitors every month still browsing with IE5.5, you should really ask yourself if it’s necessary to make the changes.

Step 4: Search the cause

Now you know about the bugs, you’ll have to look for the CSS attribute or HTML code that is causing this problem. This is often obvious. A good reference can be found on westciv.com. There is a complete list of css attributes with their support in different browsers. Too bad Firefox isn’t in the tables.

If you still cannot find the cause of the issue, search for topics on webmaster forums or post a topic yourself, with a screen shot and (a part of) your CSS and HTML code. A forum I visit often is Ozzu.

Step 5: Fix the issues

Now we’re at the essential part of making your website cross browser compatible: fixing the issues. If you know the code that is causing the trouble, find a way to rewrite the code for the specific browser. There are loads of CSS hacks to do that, but I recommend the use of conditional comments. There is an article on 456 Berea St. explaining why you should use conditional comments instead of CSS hacks.

Conditional Comments.
With conditional comments you can link to separate style sheets for all versions of Internet Explorer. A complete reference can be found on quirksmode. For example:
<!--[if IE 6]>
<link rel="stylesheet" type="text/css" href="ie6style.css" />
<![endif]-->

CSS hacks In-CSS
If you don’t want to edit your HTML file with conditional comments, see my article about CSS hacks inside your CSS file.

Transparency of Images in IE6 and lower
Internet Explorer 6 and lower will not display your transparent PNG’s correctly, there is however a simple solution using Java script. It can be found here.

And of course there are loads of other CSS hacks. There is a complete list on centricle.com, also viewing the browsers that will apply the rules.

Conclusion

Making your site cross browser compatible will cost you some time, but it’s not impossible. The is very good documentation on the web, which can help you in this process. If you use other ways to make your site cross browser compatible, please leave a comment and share it. If you liked this article don’t forget to digg or float it.