why pseudo selection code " ::-moz-selection" not working

Question

CSS
p::-moz-selection {background: #8bc34a; color: #fff;}
p::selection {background: #8bc34a; color: #fff;}

HTML
<p>The following example demonstrates how to use the ::selection element to change the color of the selected text.</p>

Answer 1

It works all right. Just select the text then the effect is visible.

Answer 2

I thought that it wasn't working too... sometimes the solution is closer and easier than I think! Thank you Seniru