function doChange() 
    {
// good names are half the code …
      var props = document.forms[0].property_type;  
// do the same with the other select
      var price = document.forms[0].price_type;  
 
// if you write incidentally = here, you’ll get an error
// besides that the code is quite explanatory now
      if ("Flat" == props[props.selectedIndex].value) 
      {
           price.selectedIndex = 1;
      }
   }

function handleChange(sValue)
{
    switch(sValue)
    {
        default:
            break;
        case 'N/A':
			document.getElementById('Buy').style.display = '';
			document.getElementById('Let').style.display = 'none';

            break;
        case 'P/W':
			document.getElementById('Buy').style.display = 'none';
			document.getElementById('Let').style.display = '';

            break;
	case 'P/M':
			document.getElementById('Buy').style.display = 'none';
			document.getElementById('Let').style.display = '';

            break;		
			
    }
}


<!-- Pop Up Function -->

   function PopupPic(sPicURL) { 
   window.open( "popup.htm?"+sPicURL, "",  
   "resizable=1,HEIGHT=200,WIDTH=200"); } 

// Flash 
var objects = document.getElementsByTagName("object");

for (var i=0; i<objects.length; i++)

    objects[i].outerHTML = objects[i].outerHTML;
	
//Clear text box
 function doClear(theText) 
{
     if (theText.value == theText.defaultValue)
 {
         theText.value = ""
     }
 }
 
 
 //Disable right click script III- By Renigade (renigade@mediaone.net)
//For full source code, visit http://www.dynamicdrive.com

var message="";
///////////////////////////////////
function clickIE() {if (document.all) {(message);return false;}}
function clickNS(e) {if 
(document.layers||(document.getElementById&&!document.all)) {
if (e.which==2||e.which==3) {(message);return false;}}}
if (document.layers) 
{document.captureEvents(Event.MOUSEDOWN);document.onmousedown=clickNS;}
else{document.onmouseup=clickNS;document.oncontextmenu=clickIE;}

document.oncontextmenu=new Function("return false")