Customizing the Sidebar – Can you help me with selectors and code?

Hello,
I started to customize the sidebar of my child theme. I found out the selectors to change the background-color, but now I’m stuck with further customization. Here is a link to my site michaeltaube.net so that you can have a look. What I want is to remove the background from the widget-title, having all spans centered, remove the background from the spans and changing the font-color of the spans to somekind of green.

When I canged the border bottom of widget-title to none in firebug it worked, but inserted into my style.css this change does not apply.

Here is the code I have for now

#secondary {
	background-color: #F9F2E7;
}

#secondary .widget {
	background-color: #F9F2E7;
}

#secondary .widget-title {
	background-color: white;
	border-bottom: medium none;
}