When I enter mog.com in the location bar, I actually go to gog.com. At some point, I think I mistyped the URL so it makes sense that it's in my history. However, I don't seem to be able to remove gog.com at all. I've tried clearing my history and editing the history by hand.
I took at a look at my hosts file and it's empty, and IE doesn't exhibit this behavior so I don't think it's a hijack in the classic sense.
The URL actually changes in the location bar, so it's not as if I enter one thing and end up somewhere else. In addition, if I search for mog and click on the the link in search results, I go there with no problem.
This leads me to believe that this is a problem specific to FF and the location bar in particular.
When i type in Mog.com i do go straight there, so there possibly could be a problem with your FF try going to Mozilla.org and downloading the newest version of FF witch would be Firefox 18.0
You can remove all stored data from a specific domain via "Forget About This Site" in the right-click context menu of an history entry (Show All History or History sidebar) or via the aboutermissions page.
Using "Forget About This Site" will remove everything like bookmarks, cookies, passwords, cache, history, and exceptions from that domain, so be cautious and if you have a password or other data from that domain that you do not want to lose then make a note of those passwords and bookmarks.
You can't recover from that "forget" unless you have a backup of the affected files.
It doesn't have any lasting effect, so if you revisit such a 'forgotten' website then data from that website will be saved once again.