(Not forgetting JSPs and Struts)
I contributed to the development and maintenance of the product. The most interesting thing I worked on was probably when I added an auto-completion field, using Ajax to suggest possible values for an input field and refine it as the user typed.
A common enough feature in web apps nowadays, of course, but fairly challenging back in 2004 or so. And it used a Struts action class to return the data for the Ajax call. Who knew you could do that?
More recently I worked on a project to modernise the GUI, converting it from its 1990s, IE-only style to a much more attractive, browser independent version, based on Twitter Bootstrap.