Thats because you are not aloud to put scripts inside your posts, as if you were a evil blogger or a multiple blog website, you could do lots of evil things.

I'm not sure if it is possible atm, but its a commonly asked thing i believe. But yeh, don't get your hopes up...

[url=http://forums.b2evolution.net/viewtopic.php?t=9349]This[/url] thread has a plugin that can allow this, but you will have to edit the plugin code to allow javascript as it's unwise in a multi user environment.

¥