First of all, if you resize a graphic, please keep the same aspect ratio. If it was initially 800x600, don't turn it into a 400x100 photo. Everything will look skewed. If you're going to reduce the width by 75%, reduce the heighth by 75% also.
When increasing the size of the photo, please don't do it until the thing gets super fuzzy. Most of us would rather see a small clear picture than a huge blurred monstrosity.
Now the last and most important thing in my opinion. Folks, please do not post photos from servers that are very very very slow. Threads simply will not load if your graphic freezes on loading. When you post a grahic that doesn't work, it can practicly kill a thread.
Ah, but apparently if the WIDTH and HEIGHT modifiers are used, the slow graphics will not cause the thread to freeze on loading.