Ampliar imagenes (sencillo)

Pegar antes de: </head>

<script type='text/javascript'>//<![CDATA[var nW,nH,oH,oW;function zoomToggle(iWideSmall,iHighSmall,iWideLarge,iHighLarge,whichImage){oW=whichImage.style.width;oH=whichImage.style.height;if((oW==iWideLarge)||(oH==iHighLarge)){nW=iWideSmall;nH=iHighSmall;}else{nW=iWideLarge;nH=iHighLarge;}whichImage.style.width=nW;whichImage.style.height=nH;}//]]></script>

Pegar en entradas:

<img src="URL_imagen" width="ancho1" height="alto1" onclick="zoomToggle('ancho1px','alto1px','ancho2px','alto2px',this);">