An easily overlooked, but important part of SEO is creating compliant markup (HTML) that can be read easily by search engines – and of course browsers. I’ve recently come across this W3C cheatsheet that provides a rather handy searchable quick reference to W3C compliant markup:
As summarised by W3C:
The W3C Cheat Sheet is an open source tool freely available for Web developers. It provides quick access to useful information from a variety of specifications published by W3C, the leading international Web standards community.
On a similar subject, don’t forget to have a read through my page about HTML for SEO.