When the window is maximized, the window does not cover the entire browser interface (the entire page size)

[clh021]

When the window is maximized, the window does not cover the entire browser interface (the entire page size)

The window is simply larger, and there is no top: 0; left: 0;

[clh021]

And Could you tell me how to set url in the windows to open the other site page? Thank you.