Remember, it is extremely important to check your site in several browsers. At the very minimum you should check it in Firefox and Internet Explorer. In fact you will most likely have better results overall if you create your site to appear properly in Firefox and tweak it for Internet Explorer rather than the other way around.
You can download Firefox for free here
http://www.mozilla.com/en-US/firefox/. If you already have Firefox, make sure you have upgraded to 3.0.
When installing Firefox, choose to install the developer tools which will help you validate your site. There are even great addons that will assist you with stylesheet work.
Just for fun - if you want to see what happens to your website in a variety of browsers, check out http://browsershots.org
The only one that completely degraded my site was a browser called Dillo. I'd never heard of that browser before and when I checked their site I found that development stopped on it over a year ago.
If you decide to check your site at BrowserShots.org, tell us about your results.