How to disable additional desktops?

I have no need of a 2nd desktop. Although sometimes a 2nd desktop is created if I open a second window, example: I am doing some sort of research and comparing results from 2 different sites, all of a sudden it creates a 2nd desktop moving one of the pages over to the 2nd desktop, making comparisons more difficult.

I find this VERY annoying. I have gone to Preferences->Mission Control->and unchecked every box there but it still happens. I have no use for Mission Control either but of course there is no way to delete Mission Control. Anyone out there have any suggestions? Thank you for any assistance anyone is able to offer.