asp.net accordion css with arrow button

I am unable to google开发者_Python百科/bing CSS for asp.net ajax accordion menu CSS [Vertical] which has arrow button on each pane. When expand it show the different arrow and when collapsed it should show different arrow.

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I use this to set the background image to act as a collapse/expand image in my website. You may have to tweak it a little:

HeaderCssClass="accordionHeader" 
HeaderSelectedCssClass="accordionHeaderSelected"

and

.accordionHeader
{
    background-image: url('images/arrow_expand.gif');
    background-repeat: no-repeat;
    background-position: left center;
    border: 1px solid #dddddd;
    background-color: White;
    padding: 3px 3px 3px 18px;
    margin-top: 5px;
    cursor: pointer;
}

.accordionHeaderSelected
{
    background-image: url('images/arrow_collapse.gif');
    background-repeat: no-repeat;
    background-position: left center;
    border: 1px solid red;
    padding: 3px 3px 3px 18px;
    margin-top: 5px;
    cursor: pointer;
}