The browser wars are over, long live the browser! Yes, browsers are responsible for rendering your website faithfully to your design, but just because each of the major browsers adhere to W3C and IETF standards doesn't mean that there aren't subtle differences in interpretation—differences that can make your web pages look dramatically different from one browser to the next.
|Firefox||Gecko||Windows, Mac, Linux||25.5%|
|Opera||Presto||Windows, Mac, Linux||1.5%|
|NetSurf||NetSurf||RISC OS, Linux, BeOS, Haiku, Amiga||*|
|Amaya||W3C testbed||Linux, Windows, Mac, Amiga||*|
* All of these together have a market penetration of about 2.0%
On top of the minor browser implementation differences, there are significant differences in computer operating systems, computer hardware, and personal user settings. These differences are often overlooked by test routines that assume everyone is running on a similar platform with state-of-the-art hardware. Consider this:
On the front-end, the browser layer is where some of the toughest programming challenges occur. Test, test, and test again. Make sure your design is rendered faithfully and that your visitors are seeing what you intended.