You can check [login to view URL] and find "modal box" link. You will notice a problem with modal box when you scroll down firs then click the modal box link. Please, fix that problem.
After you fix it, then I need you to add a locked scroll bar while modal. For instance, users can't use scroll bar for scrolling.
Make sure that modal box works for all browsers (IE, firefox, safari, and chrome)
If you have any questions about modal box then ask me anytime.
Source:
[login to view URL] - you can find modal box function by finding "function modal(clickOpen, modal)"