Simply put this means that your website needs to be compatible with the major browsers, those being Internet Explorer 6, 7, & 8, Firefox. Chrome, Safari, and Opera also come into the picture. A good place to keep up with the current percentage of which browsers are currently being used is Browsers Stats
Because of the browser incompatibility issues , many web developers make two versions of their website, one that is compatible with Internet Explorer and the other that contains Netscape Navigator specific code. These developers use a browser detection script similar to the one below to transfer the visitor to the respective site.
<SCRIPT LANGUAGE="JavaScript" TYPE="TEXT/JAVASCRIPT">
<!--
var bname = navigator.appName;
if (bname == "Microsoft Internet Explorer")
{
window.location="explorer_version.html";
}
else
{
window.location="netscape_version.html";
}
//-->
Recommended reading - Browser Detection and Cross Browser Support at Mozilla The site also includes several examples of the right way and the wrong way to implement a browser sniffer
Screen size is also a consideration as a website will look different in a 1600 x 1200 window than it will in a 800x600 window. Widescreen monitors are also changing the way websites need to be designed. Take a look at the image below and you'll get a clearer picture of the problem.
