One benefit of having valid HTML on your web site is the likelihood of your page looking pretty much the same no matter what browser is being used by your visitor. One of the problems a developer may face is lack of access to various browsers (for example, a developer using a Mac may not have Internet Explorer available). Netrenderer to the rescue! Here you can put in a web address and see what a site looks like in three different versions of Internet Explorer:

http://ipinfo.info/netrenderer/

Now if I could just find one of these for showing what things look like on a Mac! Please leave a comment if you know of one. Thanks!!