To apply structure to your HTML web pages, allowing you to specify consistent styles across a single web page or a set of web pages, the best mechanism is to use "cascading style sheets" (CSS) which are style macros supported by the browser.
CSS Tutorial rocks; spend the 15+ minutes to go through the entire thing right now.
The css specification for my website is style.css, and the one for my blog is blog.css.
Some other CSS links: