Pixelated here, and I'm so excited! I absolutely love HTML and CSS, but I have been having difficulties in CSS. For me, DIVs, classes, and IDs were almost out of reach. Not now! They are actually relatively simple, so those who wish to learn CSS shouldn't fret. Just keep at it and you'll eventually learn them.
Oh, and it's good that these are simple. They all make coding a lot easier and help spruce up your page, so I consider them a neccesity.