HTML Code and Validation
HTML is the basic language used for most web pages. You can create HTML from graphic editors like Dreamweaver or FrontPage but once you get past very basic pages you are going to need to understand the HTML code behind them to fine-tune your pages and add the functionality you want.
There is a good page load test you can use free at WebSiteOptimization
Using HTML / CSS in email
Email clients do not support HTML as well as web browsers and you can get poor results. Here are some articles that may help:
Using HTML and a detailed list of email clients and their html support levels
Tricks for getting CSS to work in html email