That same page may show clearly on IE however. IE has some format problems sometimes, so pages may come up looking weird. ALSO, it is a good idea to go back one version. If 5 is the current version, test on 4. This will help to ensure that most customers can see your webpage.
Less bandwidth is needed, so response can be quicker.
There are less resources used on the client computer, so visitors can be happier and more trusting. It can't be easily disabled. People can't see the code you worked so hard on. This is really a simple kludge, but HTML was designed for this from the beginning, It also allows you to use just about any programming language. PERL is merely a nice and complete scripting language that is widely supported.