function ventana(imagename, ancho, alto){
ancho=ancho+20
alto=alto+30
if (ancho > 790) {ancho=790;};
if (alto > 660) {alto=660;};
window.open(imagename,"Imagen","menubar=no,scrollbars=yes,status=no,width="+ancho+",height="+alto+", top=0, left=0, screenX=0, screenY=0")
}


 

  
<!-- imagenes empresa

//Pictures to switch inbetween

var Rollpic1 = "imagenes/instalaciones/img0.jpg";
var Rollpic2 = "imagenes/instalaciones/img2.jpg";
var Rollpic3 = "imagenes/instalaciones/img3.jpg";
var Rollpic4 = "imagenes/instalaciones/img4.jpg";
var Rollpic5 = "imagenes/instalaciones/img5.jpg";
var Rollpic6 = "imagenes/instalaciones/img8.jpg";
var Rollpic7 = "imagenes/instalaciones/img7.jpg";


//Start at the what pic:
var PicNumber=1;
//Number of pics:
var NumberOfPictures=6;
//Time between pics switching in secs
var HowLongBetweenPic=7;

//SwitchPic Function
function SwitchPic(counter){

	if(counter < HowLongBetweenPic){
	
		counter++;
		
		
		
		//Display pic in what <IMG> tag roll is what I called the image
		document.roll.src = eval("Rollpic" + PicNumber);
		
		//function calls itself
		CallSwitchPic=window.setTimeout("SwitchPic("+counter+")",600); 
		
		}
		
		else{
			//if its not the last picture goto the next picture
			if(PicNumber < NumberOfPictures){
				PicNumber++;
				SwitchPic(0);
			}
			//its the last picture go to the first one
			else{
				PicNumber=1;
				SwitchPic(0);
				}
	
		}

}
// termina imagenes empresa -->
  

<!-- formulario

function MM_findObj(n, d) { //v4.01
  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_validateForm() { //v4.0
  var i,p,q,nm,test,num,min,max,errors='',args=MM_validateForm.arguments;
  for (i=0; i<(args.length-2); i+=3) { test=args[i+2]; val=MM_findObj(args[i]);
    if (val) { nm=val.name; if ((val=val.value)!="") {
      if (test.indexOf('isEmail')!=-1) { p=val.indexOf('@');
        if (p<1 || p==(val.length-1)) errors+='- '+nm+', incorrecto.\n';
      } else if (test!='R') { num = parseFloat(val);
        if (isNaN(val)) errors+='- '+nm+', incorrecto.\n';
        if (test.indexOf('inRange') != -1) { p=test.indexOf(':');
          min=test.substring(8,p); max=test.substring(p+1);
          if (num<min || max<num) errors+='- '+nm+' must contain a number between '+min+' and '+max+'.\n';
    } } } else if (test.charAt(0) == 'R') errors += '- '+nm+'.\n'; }
  } if (errors) alert('Rellene los siguiente datos:\n'+errors);
  document.MM_returnValue = (errors == '');
}
//-->

<!-- Begin
function lista(form){
var URL = document.form.site.options[document.form.site.selectedIndex].value;
window.location.href = URL;
}
// End -->