In this section of Professor's Coding Corner, there are some tutorials I have written to explain some things that I had difficulty learning myself. In my years as a teacher, I found that you never REALLY learn something until you can explain it to somebody else. This holds true for website coding, as well.
Since there are many different browsers that people use to view the internet, a good web programmer tries to make sure that his site acts properly in all of them. I always check my work in three of the top desktop browsers ( Chrome, Firefox, and Internet Explorer ). Because my time is limited, I don't bother with any others.