"At this point in their evolution, Java applets are most definitely not all-purpose Web-programming tools. For this to happen, applets would have to load/run as fast as JS/VBScript/DHTML scripts. Will it ever come to pass? Possible ... but don't hold your breath."
"Given this sobering fact, I'd strongly advise you to think twice before creating a Java applet. Stick with small, fast-loading applets that do the things which applets do oh so well (and JS/VBScript/DHTML do oh so poorly or not at all)."