My web development experience is primarily using HTML, Perl, Javascript, and CSS. While I generally like to do most of the work for interactive web sites in server-side programs written in perl, with the increasing ubiquity of high quality javascript libraries and implementations, I'm increasingly favoring using javascript on the client and perl on the server working together.
This is especially true when taking advantage of an AJAX library (which abstracts away the browser specific bits so that you can concentrate on actually using AJAX). The background client-server communications and dynamic HTML techniques of AJAX applications combine to make a very exciting approach to turn interactive websites into web-based applications which are worthy of the name.