<a onmouseover="var img=document['fpAnimswapImgFP1'];img.imgRolln=img.src;img.src=img.lowsrc?img.lowsrc:img.getAttribute?img.getAttribute('lowsrc'):img.src;" onmouseout="document['fpAnimswapImgFP1'].src=document['fpAnimswapImgFP1'].imgRolln" href="URL del enlace"><img border="0" src="URL de la 1ra imagen" id="fpAnimswapImgFP1" name="fpAnimswapImgFP1" dynamicanimation="fpAnimswapImgFP1" lowsrc="URL de la 2da imagen" vspace="3"></a>