I can only watch HD videos, the non-HD video's are very blurred. What could this be?

For about 2 weeks I can't watch non-HD video on my laptop in youtube, they are totally blurry, you can't see anything. HD-Video's are running, but only from a resolution of 1080p. What could this be?

On the Internet connection, it can't be, because the HD video's run great. Have also tried another browser, that does not matter.

Yes, without HD, less pixels will be created, and less pixels will blur when looking at full screen. This is completely normal.

What does that mean, make a picture?

Maybe you are too spoiled?

Or the upload quality is just bad

Here is a picture. That's in non-HD. It seems like only a quarter of the picture is visible. Everything is wonderful in HD. I watch it in normal mode, not a full screen.

The non-HD video's are blurred, as HD video's I know myself.

EDIT: I've just watched older video's in youtube, these do not have HD and they are sharp, as I know them. Is not because of HD. Have also looked in the control panel under display and searched the net, what could be the problem, but without a solution.