You are returning false to the "onClick" event. This basically says the event has been handled, and the default handler doesn't have to do anything. If you leave it out or return true, the default action will begin. In the case of a link, the HREF action is activated.
Many people code
[font=courier]<a href="#" onclick="...">[/font]
mostly for browsers that require a HREF in a link. If the "return false" is left out of the "onclick", the browser goes to a null anchor. This will make the page jump to the top, or in some cases, reload.