Don't panic, all you have to do is add the Keyword to the URL again and then delete the original Keyword.
- Go to the URL that you want to change the Keyword for
- Click the extension and add your new Keyword
- It's fine to have two Keywords to the same URL, but if you just want one...
- To remove the original Keyword simply type 'go Lookup' into the browser
- Search for the mis-spelt Keyword
- Then click the to delete it
Watch out, if the Keyword you are changing is in a shared List which other people use then it will change the Keyword for everyone else in that List.