Visit the page http://www.mapsofindia.com/delhi/information/mcd-circle-rates.html
See the drop down. The drop down came from http://www.mapsofindia.com/delhi/information/mcd-circle-rates.js
Change in the option calls function loadXMLDoc()
Function makes an AJAX request to get the values for example http://www.mapsofindia.com/delhi/information/next.php?q=Zindpur