I'm creating a logo in photoshop, what should I make the height and width? It asks me what I want the height and width of the square where I make it for to be. Thx in advance.
Generally what you want to do is to make your logo in a vector program such as Illustrator so that you can scale it up to any size you want. If you prefer to use Photoshop though what I typically do is set it to a size that is fairly large (say 2000x1500) then zoom out to 50% so that it's comfortable to work at it on your screen. Try to stick with paths/shapes/curves/smart objects/unflattened text so that you can scale things up later if you need to make them bigger.
There is no hard and fast rule on logo size. I would recommend you create something a few times larger than what you want to be displayed on the web.
Say using 600 X 600. Have it as your master copy. When generating a copy for the web, resize it to a smaller one e.g. 100 X 100; then use the Photoshop's 'save for web or devices' function to output the actual web copy.
Having a larger master source gives you the flexibilty to generate other sizes for different usages and medias too
John is right, use a vector app first. Adobe Illustrator is the industry standard for logo design.