function MM_findObj(n, d) {
var p,i,x;
if(!d) d=document;
if((p=n.indexOf("?"))>0&&parent.frames.length) {
d=parent.frames[n.substring(p+1)].document;
n=n.substring(0,p);
}
if(!(x=d[n])&&d.all) x=d.all[n];
for (i=0;!x&&i<d.forms.length;i++) x=d.forms[i][n];
for(i=0;!x&&d.layers&&i<d.layers.length;i++) x=MM_findObj(n,d.layers[i].document);
if(!x && d.getElementById) x=d.getElementById(n); return x;
}

function MM_swapImgRestore() {
var i,x,a=document.MM_sr;
for(i=0;a&&i<a.length&&(x=a[i])&&x.oSrc;i++)
x.src=x.oSrc;
}

function MM_swapImage() {
var i,j=0,x,a=MM_swapImage.arguments;
document.MM_sr=new Array;
for(i=0;i<(a.length-2);i+=3)
if ((x=MM_findObj(a[i]))!=null){document.MM_sr[j++]=x;
if(!x.oSrc) x.oSrc=x.src; x.src=a[i+2];}
}

<a href="http://www.informaticien.be/" onmouseout=MM_swapImgRestore() onmouseover=MM_swapImage('icon_1','','img/icon1_mo.gif',1) class=boxlink target=_top>
<img src=img/icon1.gif name=icon_1 width=11 height=11 border=0>oh le joli site</a>