Red square with the number 86 in notification bar.

[Lauraweck]

I'll post a screen shot

 

[matthewkuhl]

Looks like it says 87 to me, also, it's shaped rather like a micro SD card...

 

[Javier P]

Welcome to the forums. What phone do you have? Can't you get more information about that icon if you expand the notification bar?

 

[ChromeJob]

^ This. Expand notifications, and see what it corresponds to. This is how 99.9% of notifications work IME.

I'm guessing you installed a storage space notification widget, or have it enabled in a launcher or something.

Good call, Matthew, it does look like a MicroSD card.

 

[slimchap]

I'll post a screen shot

Maybe a Class 86 SD Card.. hehehe

 

[matthewkuhl]

Perhaps it's the size or space available, or even the percentage filled?