In Firefox on Ubuntu, if I middle-click anywhere on a page that's not a link, it seems to treat whatever text is in the clipboard as a URL and tries to load it.

This is annoying, since if I either accidentally click the middle button or (more often) miss a link when trying to middle-click it, I'll either go to whatever URL is in my clipboard or get an alert saying:

The URL is invalid and cannot be loaded

Is there any way of either:

a) Disabling this functionality so that middle-click on a non-link does nothing (maybe an about:config setting?,

or

b) Making the functionality more intelligent, so that it will only try and open text if it looks like a URL (this seems like a job for a plugin).