var Pic = new Array

Pic[0] = 'charte/fr.gif'
Pic[1] = 'charte/fr_on.gif'


Pic[2] = 'charte/eng.gif'
Pic[3] = 'charte/eng_on.gif'


var p = Pic.length
var preLoad = new Array()
var i = 0;
for (i = 0; i < p; i++){
     preLoad[i] = new Image()
     preLoad[i].src = Pic[i]
}

function switchImage(whichImage,imageNumber){
   document.images[whichImage].src = preLoad[imageNumber].src
}