The coplanar faces error is because you have two (or more) 'faces' on one line. The easiest (and fastest and usually best) way to fix it is to check for errors then fix all of type (which would delete the brushes).
The plane with no normal is harder. To simplify it, it means that you took a plane and made it into a line. The best fix for this is to delete it and start over with it.
The outside world error is cause be either of two things: vertex manipulation, or a brush being 'too' close or actually outside of the 'world' (by world I mean the available creating space).
First zoom out of your map (applicable to both problems).
If it is cause by vertex manipulation then it will be extremely long. You WILL notice it. The only real solution to this is to delete it.
Otherwise, you have a brush that is too close to the edge or outside the edge, either delete it or move it.
Press Ctrl+P to check for problems (while in Hammer). This will help you a lot.