Pasted text from online contains grey, vertical rectangles - What are they, and how do you remove them?

I copied and pasted text from a website, and the text contains grey, vertical rectangles.
!http://i.imgur.com/63YYa.png

What are they, and how do you remove them? Can they be removed using regular expressions with the AltSearch (Alternative dialog find and replace)extension ?

Thanks for any information.

Maybe it is a Non-breaking space.
Try copy one and in Find & Replace, paste in Search and replace with nothing.

Better: replace with a space — see also → Highlighted black spaces?.

@manj_k one4you

If those are the non-breaking spaces, then the alternative solution is to disable the Field Shadings in “View” menu (or with Ctrl + F8).
This is better IMO because it’s done only once and preserves the non-breaking spaces which may actually be useful in the document.

If find&replace doesn’t work, I would paste it into NotePad to get rid of all formating. However, I am not sure if this helps you beyond the text example you show.