I got my MacBook Pro in December so I haven't had it for that long. After a while, on youtube the screen would act up a bit and move around or display transparent grey rectangles or a massive (transparent again) pause button. Until one or two days ago. I think it may have started yesterday or it might have been the day before. The letters displayed on the screen are just weird lines and you can't even recognise what the text is supposed to say.
I'm not sure why this is happening and also I don't know if it's something internally or just something I've installed.