I could go into all the details of how a web browser locates all the parts of a web page, but w3schools has already put together a fine page on this kind of stuff. The tutorial takes about 1 hour to go through, and when you're finished with it you should be proficient enough at HTML and web standards that you can ditch Word as a web page editor (note: Word is a TERRIBLE way to create web pages!) and switch to something a bit more capable (like notepad).
Here's the link:
http://www.w3schools.com/html/default.asp