When you are developpping Web applications that must run on various browsers, how can you test it on a single machine ?
An answer is emulation. As I am developping on a Windows machine, I have installed the PearPC emulator and MacOS X 10.3. So now, I am able to test Web applications on three different browsers : Internet Explorer 6.0, Mozilla Firefox 1.0 and Apple Safari 1.3, on a single machine.
NB : PearPC needs a really good machine to run smoothly. I recommend P4 3GHz processor at least.