Smudges on my screen

There are dark smudges in my screen (not on the screen,). What are they and what can I do to get rid of them?

Hi and welcome to the forum :slight_smile:

Is it a CRT or a LCD screen? Do you notice this problem always or only when watching a specific thing (a movie or a video or whatever)?

Did it appear suddenly? Did you install some software recently? Did you change cables recently?