For images with your logo or text content, you may get a higher quality result by using a PNGfile. Facebook also offers this helpful advice: To get the fastest load times for your Page, upload an sRGB JPG file that's less than 100 kilobytes.
I had the option to save the graphic as a .pngfile or as raw data. I actually asked myself this question the other day, and my initial answer was, "Because I have absolutely no graphic design ability at all.
Now, it's important to be careful of using PNG 24, as it has transparency issues in IE 6 and 7 and has a more heavily weighted compression algorithm, which means a page of PNG 24 versus PNG 8 is going to be much heavier.
File types: JPG, GIF, PNGFile size: 20k maximum ClickZ has their write up here and News.com over here. I am sure you have questions, such as how do I get my logo in the local results? Well here are three useful answers for you.