To JPEG, to GIF, to PNG... that is the question. Each time we create a web graphic, we engage in the "quality vs. file size" dance. To make nice and tidy, quick-loading web graphics, they need to be small in file size; however, making them small in file size reduces quality.
The trick lies in knowing which file format to use when to give you the best quality, and knowing a few tricks about each format to squeeze them down to size.