You mentioned the looks of your sites, so the above are about visual and graphic design, but good interaction design will also help making people think your site looks better, is faster, has more features etc.
Be careful whose judgement you trust. People here on HN sometimes seem to have a caricatured view of users as only being attracted to visuals. In reality, visuals can't do much more than support (or ruin) an otherwise well-designed site.
Comments
Andy Rutledge's blog has lots of good stuff. His five-part introduction to gestalt principles is about the basics of graphic design:
http://www.andyrutledge.com/gestalt-principles-1-figure-grou...
http://www.andyrutledge.com/gestalt-principles-2-similarity....
http://www.andyrutledge.com/gestalt-principles-3.php
http://www.andyrutledge.com/common-fate.php
http://www.andyrutledge.com/closure.php
For typography, Robert Bringhurst's The Elements of Typographic Style is a must-read. http://www.amazon.com/Elements-Typographic-Style-Robert-Brin....
You mentioned the looks of your sites, so the above are about visual and graphic design, but good interaction design will also help making people think your site looks better, is faster, has more features etc.
Be careful whose judgement you trust. People here on HN sometimes seem to have a caricatured view of users as only being attracted to visuals. In reality, visuals can't do much more than support (or ruin) an otherwise well-designed site.