Because not all people use the same browser, it’s not enough to test a design on only one of them. What’s worse, some people don’t even use the latest version of their browser, so we also have to test different versions. So here’s a list of most common browsers and links on where to download them (including older versions).

Mozilla Firefox
You can download different versions on Mozilla’s FTP server. Select your version and your operating system. As long as you don’t overwrite another version, you can have any number of versions installed. To run multiple versions at once, I believe you need to run each one under a separate profile. I usually check websites on 1.0, 1.5 and 2.0, but there are rarely any differences between versions. Camino, Netscape and Galeon use the same rendering engine so they will show sites as Firefox does.

Internet Explorer
This one is windows only. Linux users can use Vmware or Wine to install it, mac users can use VirtualPC on Ppc or Bootcamp/Parallels on Intel machines. I myself use a remote desktop connection to a Windows machine. You can install IE7 on your Windows (via Windows update) and use standalone versions of older versions, found here. These require no installation, just unzip the folder and run the exe. I can confirm them working on windows XP but can’t tell you about older Windows versions. To solve cookie and conditional comments problems with standalone versions, see here. I tend to make websites look ok on 5.5 and higher versions (since even Microsoft doesn’t make websites for older versions).

Safari
Apple offers only the latest (beta) version of their Safari browser, But click here to download any of the older versions. Some versions may not work if you’re not running the latest version of OS X, but everything seems to work fine on Tiger. Testing on 2.0 is recommended since 3.0 is still beta and it doesn’t automatically update. I do believe Omniweb and Shiira use the same rendering engine as Safari does.

Opera
You can download the latest version of Opera for your system on their website, but older versions can be found here. Again, if you don’t overwrite an older version you can install as many as you like. I usually test versions 8 and newer, since Opera 7 doesn’t really show up in statistics.

Konqueror
Linux users get Konqueror with their KDE. Mac users can also install KDE and use Konqeuror. Windows users can probably install KDE on Cygwin, but I haven’t tested this myself. How to get different versions is a mystery to me, but I’ve found Konqeuror to be the most standards-compliant browser, so if your page works on every other browser without hacks, it should work on any newer version of Konqeuror. Also, I believe that Linux users do upgrade their software regularly.

Lynx, screen readers
Lynx is a text-only browser for Unix that works in a command line environment. I guess Linux users know how to install Lynx… Mac users can find it in Fink, Windows users can give this a try. Lynx won’t render any css or tables, so I do recommend writing semantic code. Also note that people with bad or no eyesight use screen readers to “view” websites, so Lynx is your best approximation to this.