Why can't I use scripting languages or Flash in my styles?
Short explanation: It's a security problem.
Long explanation: Since users can login to LiveJournal and have their login username/password saved, if we allowed either scripts or Flash, people could write scripts to intercept the username/password and save it, or email it to the malicious script author. We've looked into solutions to allow scripting and Flash, but there seems to be no good way to prevent them from having access to login information (cookies).
If you know of a robust way for us to allow scripting or Flash, please let us know! For now, though, all scripting and all Flash is removed from journal styles and overrides before it's sent to any browser.
Its in my (limited) understanding that flash is not a scripting language, thats why I didnt lump flash in with general scripts. Feel free to add your own edits, I'm just a newb, dont know too much yet.