The web is a difficult animal to wrangle. A web page may appear different in different web browsers. For this reason, as a web page designer, I keep various web browsers like IE, Netscape 4 and Netscape 7.
Being a professional in the world of web page design, I think it is important to be aware of the software products that might somehow impact my work. Have installed lots of software program demos relating to graphic design, broken link checking, site stripping, etc. Several of the free, useful ones and a few of the paid for ones continue to grace my installed programs list.
Knowing about the new web browsers that might shake up the big 2 (Microsoft and AOL-Netscape) is very much so part of my job.