How to get an image onmouseover

I am using an image by default But i need the imag开发者_开发百科e only when i am doing my mouse over option

This is the div In which Ihave the image

<div style="float:left; height:90px; width:90px; background-color:#CCCC99" 
 style="display:block" onmouseover="return mouseOver();" >
 <img src=<?=base_url()?>images/m11on.gif name=b1 width=90
  height=80 border=0 onmouseover=mouseOver() onmouseout=mouseOut()></div>

On mouse out my div must be empty This is the javascript function i am using but it doesnt seems to work properly

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<div onmouseover="this.innerhtml='<img src=\"imgurl.jpg\">'" onmouseout="this.innerhtml=''"></div>