Rusty wrote: If you are going to upload as an image put into a post (as you did), it is 500px on the longest side. If you are going to put something into your gallery (you should set one up, Weez), around 800-to-850 on the longest side works pretty well.
Rusty
In addition to the 500 pixel length restriction, I believe you get up to 500kb. My images are usually around 200 - 300kb, but anywhere in the 100KB range gives good results too.
Courtney