Web design and layout is tricky. Even if you use good standards, things that look great in one browser are likely to look terrible in others. My development process used to involve a 'compatibility day' where I would fire up my old Windows 98 Dell and try everything out in various old browsers.
Now I don't have to do that anymore. The Dell can go back to being used for playing European Air War.
Browsershots.org is a website that takes a web address and gives you screenshots of how the page looks in dozens of browsers. The site is free and open source, although you can get your results more quickly if you give them money. Even without the donation, most pages show up in just a few minutes. They cover Internet Explorer 5 and Netscape Navigator, as well as obscure Linux browsers I've never heard of such as Iceweasel and Kazehakase.