Under some conditions autofill fills to the left and right of the typed character, and incorrectly overwrites typed characters. In most cases it substitutes a 'w' for an 'h'. Steps to reproduce 1. In about:config, browser.urlbar options should be default, except: browser.urlbar.autofill true. Specifically: browser.urlbar.autofill true (nondefault) browser.urlbar.autocomplete.enabled true (default) browser.urlbar.trimURLs true (default) browser.urlbar.defaultbehavior 0 (default) 2. In the URL bar type https Results For example, on this computer, after the first character the 'h' is overwriten and you get 'webmail.primary.net'. If you continue typing you get 'wttps'. If you set browser.urlbar.defaultbehavior to 4, the problem does not occur. Other information Problem does not occur with a new profile. You need sufficient history to have the right URL to fill in. Also, it may not be 100% reproducible on all profiles, for reasons I don't understand. The problem occurs on both Windows XP and Ubuntu Linux.

For the record, I think it's also a duplicate of bug 559878, but it doesn't matter, since they're both still open.