I have always been much more worried about how the software that I write works.    Stability, accuracy, scalability, etc were always much more important to me than the choice of font, color, filters on the images, etc.

Recently I have had several people tell me that it doesn't matter how well a piece of software works.   If it doesn't look sharp, it will loose some credibility.    Let's face it, most people don't get to see the most impressive aspects of the software we write.   

Having thought about it more, if our software doesn't look impressive, it is less likely to be seen as impressive or taken seriously.

With this in mind,  I have started the task of trying to understand the UI and style sheets.   It is a worthwhile endeavor.

Some of the resources that I have found useful, you may find useful as well.

http://www.csszengarden.com/

http://www.w3schools.com/css/default.asp

http://stopdesign.com/articles/throwing_tables/

http://stopdesign.com/articles/absolute/index.html

What other style sheet resources have you found useful?