The website 'cpumag.com' is a simple redirect to 'computerpoweruser.com'. 'cpumag.com/idealbb' is therefore a redirect to 'computerpoweruser.com/idealbb', which then redirects to the correct index page for the IdealBB forum on the server. However, entering 'cpumag.com/idealbb' does not redirect to 'computerpoweruser.com/idealbb', and therefore instead of being redirected to the correct index page, you are redirected to an IdealBB error page. Entering 'cpumag.com' in the address bar correctly redirects to 'computerpoweruser.com', however. I don't have much behind-the-scenes HTTP knowledge, but I did some packet sniffing and it seems that for some reason, after Webkit receives a 301 code and does a GET on the URL of the new location returned (which, it seems, it the exact same URL, 'cpumag.com/idealbb'), the response from the server (302) gives a location of 'cpumag.com/idealbb/error...', instead of a location of 'computerpoweruser.com/idealbb/redir...', which then redirects the browser to the forum. Accessing the forum via 'computerpoweruser.com/idealbb' with Webkit works properly; the 302 response gives the valid URL. Also, I can access the forum via 'cpumag.com/idealbb' properly in both Firefox and Opera, and the 302 response from the server for these browsers gives the proper 'computerpoweruser.com/idealbb/redir...' URL. Not sure if this is an IdealBB issue or Webkit issue but since Opera works, I'll just assume it's a Webkit issue. I've seen a few bugs (#17692, #17868) that look like they could possibly be the same issue, but I'm not positive.
I'll also add (though it's already been reported before, I believe) that accessing the page via 'computerpoweruser.com/idealbb' executes multiple redirects, whereas FF and Opera does not.
I cannot reproduce this with shipping Safari 3.1.1 on Mac OS X 10.5.3, or with a local debug build.
I'm on OSX 10.4.11 and it happens on the latest nightly as well (June 9). You are able to access the forums (and not an error page) by going to 'cpumag.com/idealbb'?
Yes, this URL gets me to the CPU forums page. This could be a Tiger-only issue, since much of this code is not in WEbKit, but in system frameworks. I don't have access to Tiger to check that right now.
At the time of writing, http://computerpoweruser.com/idealbb http://www.computerpoweruser.com/idealbb seem to be not valid as examples. Using WebKit-SVN-r38064.dmg on Mac OS X 10.5.5.
Can no longer access the website and it seems unlikely this is still an issue.