?pwd=WhatsInTheForm

And just because you don't see a login error doesn't mean it isn't being passed to the web server. Change it from post to get method and you'll see it.

In other words I'm looking for a URL that allows me to directly log into the account by only substituting the username and password. If it helps, I can give you the name of the site too. It's one of those blogging sites.
You'll notice that I slowly moved on to more high profile domains. If it isn't government or big business then I don't even bother anymore.