HELPP. My monitor keeps turning off every 10 minutes?!?

Okay. So. I have Windows Vista. & I'll be on Facebook or something and all of a sudden my monitor turns black but the light around the button is still on. So I'm like, Hmm. Okay I'll just turn it off then back on. I do that & it freaking does it againn. I probably did it 7 times (literally) before the monitor showed up again. So now instead of doing it over & over I just turn it off and wait like 5 minutes before it actually stays on. So I searched Google and all I got was to go to 'Adjust Screen Resolution' ; 'Advanced Settings' ; then click the monitor tab and change it to at least 75 Hertz to reduce monitor flicker. I do that & it still does it.. please help. It's getting worse & worse. It did it 3 times while trying to type this it's so fustrating.