There are many places you can go on the net to see statistics about which browsers support which tags, and sometimes even how they are supported. But none of them can give the perspective of precisely how it appears to the user with that browser. Not without actually downloading it, installing it, and viewing the site in question yourself.
At Algonquin Studios, we make every effort to build sites that are accessible. Since many clients need e-commerce sites which are usable by as many people as possible, this may be a tall order to fill if you don't have the experience hand-coding your HTML through all the different browser versions that have come out since the spawn of the web. Sometimes the only way to guarantee that a site is accessible to a user of Mosaic 3.0 is to install Mosaic 3.0 and view the site yourself.
Given our focus on usable sites, I began to build my browser archive, now uploaded to browsers.evolt.org, to ensure that the sites my company built would truly be usable, and not potentially usable based on imprecise data provided by third parties.
You will note many archaic browsers in there, more than you would expect to see in a normal testing process, but that is a testament to how this took on a life of its own. More accurately, I needed a hobby, and this became it. So, don't be surprised to find Netscape Navigator 0.9 and Netshark 1.0 as well as Internet Explorer 5.0 and some of the latest Mozilla builds. That's just how these things go when they get out of hand.
And so I hand my browser archive over to evolt.org, and free myself of the burden (actually, I'll still be maintaining it, so email me if you have some to add). Please feel free to add browsers or versions that are missing, since even at over 80 independent browsers (and many versions of most), there are still holes in what is represented. Of note, are non-MS-Windows versions of almost anything other than Navigator or Internet Explorer.