Question

I am actually do not even know hot to define this, but I need to change the text background color. Never did this. Now when I am selecting the text, lets say pressing the left mouse button and marking a proportion of the text all the background becomes red, so I do not know what element defines this property.

Answer 1

You are probably looking for this (note double : is correct):

::selection {color:#fff;background:red;}
::-moz-selection {color:#fff;background:red;}