var LARGEUR = document.body.clientWidth;
var LECRAN  = screen.availWidth * 0.75;
var HAUTEUR = document.body.clientHeight;
var HECRAN  = screen.availHeight * 0.75;

if((LARGEUR < LECRAN) || (HAUTEUR < HECRAN))
{
window.moveTo(0,0);
if (document.getElementById || document.all) 
  {
  window.resizeTo(screen.availWidth, screen.availHeight);
  }
else if (document.layers) 
  {
  if (window.outerHeight<screen.availHeight || window.outerWidth<screen.availWidth)
    {
    window.outerHeight = screen.availHeight;
    window.outerWidth = screen.availWidth;
    }
  }
}