flex css transparency

I'm trying to make the background of all tabs from a TabNavigator completely transparent (via CSS), but somehow I can't get this done correctly.

This is what I've got so far:

TabNavigator
{
    tabStyleName: "tabNavTab";
    fillAlphas: 0, 0, 0, 0;
    backgroundAlpha: 0;
    focusAlpha: 0;
    bor开发者_C百科derStyle: none;
}
.tabNavTab
{
    fillAlphas: 0, 0, 0, 0;
    backgroundAlpha: 0;
    borderStyle: none;
    focusAlpha: 0;
}

But the tabs still have borders and the inactive tabs still have a tiny gradient from white to transparent.

What am I missing?

edit:

I got it. I have to set the upSkin, downSkin... properties, too!

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I always recommend the use of the style explorer:

http://examples.adobe.com/flex3/consulting/styleexplorer/Flex3StyleExplorer.html

Helps me with almost all of my CSS issues.