1. Always use strict doctype and standards-compliant HTML/CSS
2. Always use a reset at the start of your css
3. Use -moz-opacity:0.99 on text elements to clean up rendering in Firefox, and text-shadow: #000 0 0 0 in Safari
4. Never resize images in the CSS or HTML
5. Check font rendering in every browser. Don't use Lucida
6. Size text as a % in the body, and as em's throughout
7. All layout divs that are floated should include display:inline and overflow:hidden
8. Containers should have overflow:auto and trigger hasLayout via a width or height
9. Don't use any fancy CSS3 selectors
10. Don't use transparent PNG's unless you have loaded the alpha