Tales of a Code Monkey: A preview of gtk-vnc v0.3.3:
"At first, a VNC web-browser plugin may sound like a silly idea. Of course, both RealVNC and TightVNC ship a Java applet VNC client. Clearly, there is demand for embedding a VNC session within a web browser. Besides the obvious concerns about performance, Java applets are severely limited in what they can do. You cannot grab the mouse and you cannot grab arbitrary key events. You really can't build a first class VNC client as a Java applet.
With a gtk-vnc based plugin, you can have a first class VNC client in your web browser."