It’s not easy to remember the multitude of html tags and their attributes, so it’s good to have somewhere to go for a quick recap.
My favourite site for most HTML help is Your HTML Source, which has a great glossary of HTML tags. It clearly outlines the correct usage for the all the common tags and many you might not normally think of using.
It’s a good idea to use an existing tag if possible, rather than defining your own class, as it makes your code more compliant with web standards and screen readers.