Changing the CSS

I wish to style the widgets that come with wordpress.
For example, I want to change the background behind the words Featured bar on my website urban-fix.co.uk
however, when i make the changes in firebug it works, i then go and add it to my custom css and nothing happens…
I am knew to this so i know i am doing something wrong…
I have got rid of breadcrumbs and the category/tags on listing pages so im not completely incompetent! haha.

Another example is i wish to change the way the dashed lines look.
so i added this to the custom css, which should make them black and 3px. but no joy!
.geodir_category_list_view li {
border-bottom: 3px #000000 dashed;
padding-bottom: 15px;
margin-bottom: 15px;
display: block;
list-style: none;
}

Any quick pointers would be great!
Thanks