Stop making your websites go to full screen automatically! I mean it. Stop it.
People do not take into consideration how different website users set up their operating system, software and hardware.
First, making a window auto maximize without giving the user the option to do it or not is irritating.
Second, making a window auto maximize without giving the user notification what will be happening is inconsiderate.
Third, not every user has a single monitor. Many users have set ups with multiple monitors. It allows them to work on more than one application at a time more efficiently. When a window goes to full screen, it spans all monitors—not just one. Since most full screen designs are centred horizontally and vertically, the content ends up being split evenly between both screens, with the left half being on the left monitor and the right half on the right monitor. If the first two issues I listed above were irritating and inconsiderate, this issue is very irritating and very inconsiderate.
Don’t make designs that expand to full screen automatically. Give the user a choice. If you have to make it full screen, at least learn how to constrain it to a single monitor.