mouseover event on xul menubutton

I want to change the display of the button on the mouse over event of the menu button. It shows the button border on the mouse over event of the menu-button and also the separation of the button and the drop down.

<toolbarbutton id="search" type="menu-button" label="SEARCH" width="83" height="25" oncommand="webSearch();event.stopPropagation();" onmouseover="">
   <menupopup>
      <menuitem label="Web" value="webs"开发者_开发百科 oncommand="webSearch();event.stopPropagation();"/>
      <menuitem label="Images" value="images" oncommand="imageSearch();event.stopPropagation();"/>
   </menupopup>
</toolbarbutton>

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What do you want it to do? You can add some CSS to change it's style when you hover over it?

#search:hover {
   /* your styles here */
}