Internet Explorer thinks it's my phone

I'm sorry to have to ask such a silly question but I have searched everywhere for an answer before posting this. I use my phone to visit many websites and watch videos. Now, when I visit those same websites and try to watch videos on my computer, it still thinks it is on my phone and I can't get it to go back to normal. For instance, when I watch a video on my computer now, it is half screen and black & white. The buttons don't line up so you can't click on them. You have to guess where they would be on a full screen and click over there. I know there is probably a really simple answer - please help...