function VecImagenes()
{
  n=0;
  this[n++]="images/fotocentral_001.jpg";
  this[n++]="images/fotocentral_002.jpg";
  this[n++]="images/fotocentral_003.jpg";
  this[n++]="images/fotocentral_004.jpg";
  this.N=n;
}
var Imagenes=new VecImagenes();
src= Imagenes[ Math.floor(Math.random() * Imagenes.N) ] ;
document.write("<IMG SRC="+src+">");