Tabs not automatically closing and are sitting open on my screen

[AC Question]

Sorry, didn't know how to word my question. I've used my data allowance up, think this is due to all tabs I have used or looked up, aren't closing down automatically as they used to n r sitting on my screen, I need to use the square at the bottom right of the screen , click on it n close each one down individually, does this make sense n can anyone help? Thanku