How do you get rid of 404 error when viewing Joomla home page?

I'm still learning Joomla at the moment and have been making a lot of changes just to see how everything fits togther. I have though now managed to get to a position where when I try to preview the site or load the default home page I get a 404 page not found error - arrrrgggghhh.



Interestingly all the problem is the fact I do not have a default menu! Have a look at your main menu and double-check that you have a default item. Reseting solved the problem. I have since tried to replicate the problem by creating a new menu, making it the default and then trying to deleting it - and then in theory leaving me without a default menu but Joomla caught this and wouldn't allow the deletion, so I'm not sure how this happened!

Initially I tried to search for a resolution by looking for 404 errors but of course this results in millions of messages. I'm just going to post another entry relating to debuging which assisted the solution much more quickly.