How to fix ? All pages but the homepage show 404 errors

All your pages except the homepage are giving 404 errors ?

If you are using self hosted Wordpress just login into your admin account Go to Settings - Permalinks

Now change the permalink structure to default !

Check your links now and it should be working ! If it works restore your link structure back to your liking!

Hope this has helped ! Do give in your comments if it worked for you.