Changes on style.css not taking effect.

Hi there,

I'm trying to add simple customization on Blogs MU using its child theme css..

So i did something at the end of style.css of the child theme..
I'm not sure if i've done it wrong. I'm just new here..

/* Custom Styles */
#top-bar {
margin-top: -20px;
}
#top-bg {
padding: 5px 0;
}

Just some simple tags but it didn't work and so i use a plugin called CSS and JavaScript toolbox and it did work to update the CSS of the theme. Is there anyway i can do it in style.css of the child theme so that I won't have a lot of external css for the site.

Thanks!