HTML stands for H yper T ext M arkup L anguage. A language used to describe structured documents which may have links to other documents. HTML can be found on any web page. All the popular browsers have a View Source option, so if you find a page which does something you want to do, view the HTML source and see if you can work out how it was done. Because browsers vary in several ways, you cannot assume that your page will show up as you intended in other peoples' browsers just because it displays correctly in your own browser.
Style sheets are the best solution.
Beginners may want to check out the Guides and Tutorials section.