31 Days of my XTi | Day 11 - Purchasing a new lens

I have a few lenses, and while looking into getting another I found out a piece of info that is actually kind of important when you are investing this kind of money. If you know already that you plan to upgrade your camera to one of the professional ones, you have to pay special attention to the lenses you buy. I am told that you cannot use an EF-S lens on a Canon 5d mark II. So that kit lens...no go. I suppose by then you will be investing in more expensive equipment all around anyway, but I'd like to make my money stretch.
EF-S lenses line up with the white square on the front of the camera, and EF lenses line up to the red dot, so if you are actually looking at a camera body and trying to decide if one or both types of lens will work, look for those. If there is only the red dot the EF-S lens will not work.
I looked up why this is, and the answer is a lot of technical stuff that breaks down to the EF-S will damage a professional camera because there is a shorter distance between the lens and the sensor.
If you plan to upgrade to a 7D both types are compatible, so you don't need to be as concerned about that aspect of your purchase.
I hope this info is useful to someone, because I know I had no idea that all canon compatible lenses don't actually go on all Canon cameras!
If you have any tips or extra info please leave it in the comments!