As a web developer you should be making sure your sites work in multiple browsers. Hopefully you are striving to comply with XHTML standards, to minify cross browser issues. Maybe you are working on an intranet site, where you can control which browser is used, but it only takes a few seconds to look at how you site renders in different browsers. As a rule of I try to support IE 7, IE 6, Firefox 2, Firefox 3 and Safari.
Cross Browser Testing Tip 1:
Check out Browser Shots. Its a site that allows you to enter a URL and it will produce an image of how the site renders in over 100 different browser versions.
Cross Brower Testing Tip 2:
Cross Browser Testing Tip 3:
Creating automated tests can save you time in the long run. Tools such as WatiN allow for tests to be created using different browsers
using (IBrowser ie = BrowserFactory.Create(BrowserType.InternetExplorer))
ie.TextField(Find.ByName("q")).Value = "WatiN";
using (IBrowser firefox = BrowserFactory.Create(BrowserType.FireFox))
firefox.TextField(Find.ByName("q")).Value = "WatiN";