onmouseover问题
<div id="Layer4" onMouseOut="this.style.background-color='#93bee2';" onMouseOver="this.style.background-color='#0033CC'"; style=" width:22px; height:22px;border: 0px #B1C8FF solid;"><img src="biaoqing/2009426204649332.gif" alt="表情" width="22" height="22" onClick="MM_showHideLayers('Layer5','','show')" ></div>可是背景没有变化，请教
