If you've never worked with pop-up windows before, you might want to experiment with different sizes and options. Naturally, whatever attributes you choose will depend on the size and nature of the document you want displayed in the pop-up window.

For example, if you're including a rather long document, you would definitely want to include scrollbars. On the other hand, if it's just a few help document sentences, scrollbars wouldn't be necessary as long as your width and height attributes are appropriate.