Login from Homepage/Other Pages

Hi all,

I'm currently trying to figure out how to implement a login/logout link on my homepage that changes depending on whether or not they're logged in and also shows their username when they are indeed logged in. The forums are located in the /forum directory, but having access to this feature in our site's header that spans all pages, not just the forum pages, would be awesome.

Our site is just HTML, not on a CMS like Wordpress.

I'm sure there's a fairly simple solution for this, but I cannot seem to find it.

Any help would be appreciated. :)

Thanks for your time.