Let us discuss cross browser testing in more practical and ideal scenario.
Mostly widely used browsers are IE and then Netscape...So while doing your tests in both these browsers, dont just forget the Internet options you have in the browser settings..
Say, enabling/disabling java scripting, debugging,etc..and then u carry out ur testing..You ll find the major difference..You know how ? Because IE and Netscape are not that matured of handling java script errors. But Netscape somehow gives u meaningful message whereas IE never gives meaningful message..So goes on.....this is just a basic to start with..So many things r there...
You could mail me to email@example.com for further doubts..
The first thing that you could do in a cross browser testing is to sort out which browsers you would need to support and specifically which versions also. It so happened that once we generaly said that we would be supportin our application on IE and Netscape but we tested with IE 6.0 alone and some of the features didnt work in IE 5.0. So better clear that off and then start testing