This is one of the most irritating things that someone, i.e., a website I visit, can do to me:
resizing my browser.
Who the hell do you think you are? This is my browser!
Fortunatley, Firefox can prevent this easily:
Tools -> Options -> Content
in front of “Enable JavaScript”, click “Advanced”
deselect “Move or resize existing windows”

Thanks for this tip! Resizing my browser window is highly annoying. It’s nice to know I can control it. Yeah, Firefox!