>>2941
The web is mainly HTML, CSS and javascript. Each have their unique purposes. HTML puts elements on the page, CSS decorates them and Javascript let's you do advanced stuff like create a program which generates prime numbers (and also dynamically update HTML and CSS, that's pretty important). All javascript is client side so if a user did say, run that prime number generator, all the computing would be on their end.
Some things need serverside like have a message board or account feature, you probably also need SQL.
Also theirs a bunch of other stuff like AJAX and JSON and XML. I'm just writing a vague summary.