I'm surprised there haven't been more questions. Let's see... I got stuck on 7, then 13, then 17 was a bit of a challenge. From 19 on it's been pretty good and challenging, though some were really easy as they followed on the same thought-path as the previous puzzle.
If you are thoroughly stuck, I recommend the following:
1. Don't look up any spoilers. At least not yet!
2. Go away and try again tomorrow, or later on. When your brain's had a rest, it'll have a better chance.
3. No really, give it a break.
4. Ok, start over on this puzzle. Erase your previous guesses from your mind.
5. What clues are you given? If you don't see a clue, go back to the previous page and compare it to this. What has changed?
6. The easiest way to compare is to view the source for the page. By the 20 puzzle, you ought to be pretty familiar with what the source for this puzzle looks like.
7. Did the clue not help too much? Try a little creative googling (but not for the spoiler! You can still figure this out!)
8. Once you figure out what direction the clue's pointing in, you're good to go.
9. Still stuck? Not even a vague idea? Alright, you can look up some hints. Ask here in the comments, read through my earlier posts, or follow the link to the digg conversation - but be very careful, it's full of spoilers! You won't be nearly as happy if you find something that gives it away. I like to start with gentle hints first. I'll put out the gentle hint guide once I complete the puzzle.