Tiny grey squares

There are a couple of tiny grey squares on the upper left corner of my files. One has a "01" and the other one a symbol which I don´t know what it is.
They appeared today (obviously I clicked something without noticeing it).
Any hints?

Press Cntrl H to hide em. Its just the slices showing. Very annoying and drives me crazy.

Slices are on. Do View>Show>None.

Thank you guys, now I know another way to hide slices. I usually hide them in my stomach (I´m talking about pizza slices, of course).
By the way... what are the slices???

Slices are what people use to cut up an image then save it as an .html file. For example I have a picture of a dog that has text around it. I want the text to each be part of the navigation. So you would slice it up, etc then it would be a site layout.

I agree those are annoying to have. You can remove it altogether .. View > Show > Show Extras Options.

Uncheck Slices.. Or choose those you don't want.