Modal Windows: If you put up a modal window, and it blocks content beneath it, and I can't at least move it out of the way, then it 100% is anti-user behavior. There is NO good reason for blocking the user from seeing content that might be relevant to the modal window. This is true for both websites and apps.
Compare Safari's Open File to Chrome's Open File. Chrome's Open File modal cannot be moved. Safari's can.
If you have a modal, and it blocks content, you have to be willing to say "I want to prevent my users from seeing this content while dealing with the modal. The content that is being blocked is not important, and it serves NO purpose."
Compare Safari's Open File to Chrome's Open File. Chrome's Open File modal cannot be moved. Safari's can.
If you have a modal, and it blocks content, you have to be willing to say "I want to prevent my users from seeing this content while dealing with the modal. The content that is being blocked is not important, and it serves NO purpose."