i want to populate drop down box values on the basis of other drop down box value dynamically(without refreshing the page) using java script. i tried to search on google, but could not find anything. please can anybody help me in this regards.

Thanks

This can be achieved if you prefer using AJAX in your page. To get the basic of it, here's a simple demo for you.
This example comes in 2 separated html document: the main.html which holds the entire script, and the request.html that holds another options and will be injected to the main.html upon request.
Here's the code for the main.html:

<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
   "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
<head>
<meta http-equiv="X-UA-Compatible" content="IE=EmulateIE7" />
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<meta http-equiv="Content-Style-Type" content="text/css" />
<meta http-equiv="Content-Script-Type" content="text/javascript" />
<title>JavaScript Demo</title>
<script type="text/javascript">
// <![CDATA[
/* No editing required -
   For demonstrational purposes only. */


// Declaring variables
var ajax, update, xmlData, getOptions;
var obj, select, option;

// This is a simple prototype that will skip the long declaration of ( element.getElementsByTagName( tagName )[reference] ).
// And now can be defined as element.obj( tagName, reference )
obj = Object.prototype.obj = function( tn, ref ) {
   if (( tn ) && ( typeof ref === "number" ) && ( ref !== null )) {
   return ( this.getElementsByTagName( tn )[ ref ] );
   } else {
   return (  this.getElementsByTagName( tn ));
   } 
};

// This is the function reference which is the one who handle's and process the request sent by the XMLHttpRequest object.

// And considered as the most important part of the whole program. 
getOptions = function() {
select = xmlData.responseXML.obj("select", 0)
option = select.obj("option");
oLen = option.length;
   for ( x = 0; x < oLen; x++ ) { document.obj("select")["lists"].remove( x );
document.obj("select")["lists"].add( new Option( option[x].childNodes[0].nodeValue,  option[x].getAttribute("value") ), x );
   }
};

ajax = function ( url ) {
xmlData = null;
   if ( window.XMLHttpRequest ) {
   xmlData = new XMLHttpRequest();
   } else if ( window.ActiveXObject ) {
      try {
      xmlData = new ActiveXObject("Microsoft.XMLHTTP");
      } catch( e ) {
          xmlData = new ActiveXObject("Msxml2.XMLHTTP");
      }
   }
   if ( xmlData !== null ) {
   xmlData.onreadystatechange = getOptions; 
   xmlData.open("GET", url, true);
   xmlData.send( null );
   } else {
     alert("\nYour browser does not support AJAX Request!"); 
   }
};

update = function( sel ) {
sel = ( document.getElementById ) ? document.getElementById( sel ) : document.all.sel;

index = sel.selectedIndex;

ajax( sel.options[index].value );
return;
}
// ]]>
</script>
</head>
<body>
<div id="content">
<form id="ajaxForm" action="#" onsubmit="return false;">
<div>
<select id="lists" name="lists" size="1" onchange="update( this.id );">
<option value="">Default List</option>
<option value="">Default List</option>
<option value="">Defaut List</option>
<option value="request.html">AJAX Demo - Request Lists!</option>
</select>
</div>
</form>  
</div>
</body>
</html>

And this goes for the request.html

<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
   "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
<head>
<meta http-equiv="X-UA-Compatible" content="IE=EmulateIE7" />
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Request Page</title>
</head>
<body>
<div id="content">
<form id="frm" action="*" onsubmit="return false;">
<div>
<select id="sel" name="sel" size="1" onchange="ajax.listed(this.id);">
<option value="">Requested List</option>
<option value="">Requested List</option>
<option value="">Requested List</option>
<option value="main.html">AJAX Demo - Default Page!</option>
</select>
</div>
</form>
</div>
</body>
</html>

Hope you find it useful...

Let you have two combo one is for supplier & another one is for products. When user select a supplier then you wants populate product combo. Am i right?

<select name="supplier" onchange="products(this)">
.................................................................................

NOW WRITE THE products METHOD LIKE:

function products(supplier) {
    var prodcombo = supplier.form.elements["productcombo name"];
//remove previous data    
while (prodcombo.options.length) {
        prodcombo.remove(0);
    }
    var choice = supplier.options[supplier.selectedIndex].value;
................................................
// Now you got both combo. So populate.....
}
This question has already been answered. Start a new discussion instead.