#1: Archive URLs: All too often, websites change URLs (web addresses) of pages when they are outdated and move off the main page, into archives. This can make it extremely difficult to build up significantly good search engine placement, as links to pages of your site become broken. When you first create your website, ensure you do so in a manner that allows you to move content into archives without having to change the URL. Popularity on the web is built on word of mouth, and you will not be getting any of that publicity if your page URLs change every few days.
#2: Alt and title text
: Ensure you make use of the alt and title attributes for every XHTML tag on your website that supports them. This information is of critical importance for accessibility when the website is visited using browsers that do not support images, and when more information than the main content might otherwise be needed.