How to build a good Web Look and Feel Standard

I'm working on a large web project based on LAMP stack.

I have to create a 'look and feel standard' for the aplication and i don't know how to begin. What parts must have this standard? Is somewhere a model?

I don't have large experience on web development so maybe i need to inspire in some good sta开发者_如何学Cndards. Do you know where can i find some standards?

Thank you very much :D

The jQuery UI ThemeRoller provides a great GUI for playing with their stock themes, or customizing them. Worth while investigating.