Anyone know how to add a passcode so that when people tries to view ur LJ they are prompted for a password?

I haven't seen this feature implemented any any livejournal before; do you have an example to show that it can be done?

Also, instead of using a passcode as you call it, you can use custom friend filters on your entries.

i ve seen some from bloggers that whenever a someone tries to enter the blog, a command prompt pops up, asking for a password before that blog can be viewed.

So LJ doesn't have such a code?

I'm pretty sure that livejournal does not have such a code, since livejournal does not allow javascript; (I think) Blogger does, though, which is why password protected blogs are allowed there. Sorry!