login page background

I put the code to change background Login page, but do not work, and also want to know to to change panel color or make transperent??
p.s.: the same code worked to Body of otheres pages.

here is the code that I used...

/* login page background */
body.function-login
{
height:100%;
background:transparent url(../images/Background_1024.png) no-repeat center center fixed;
background-size:cover;
}