// JavaScript Document

var selectedDiv="block_01"; // set first visible block

function swapBlock($block) { 

	if(document.getElementById($block).style.display == "none"){

		document.getElementById(selectedDiv).style.display="none";
		document.getElementById($block).style.display="inline"; 
		
		if( $block == "block_01")
		{
			document.getElementById("thumb_02").src = "images/btn_residential.gif";
		}
		else{
			document.getElementById("thumb_01").src = "images/btn_commercial.gif";
		}
		
	}else{

		//document.getElementById($block).style.display="none";
		//document.getElementById(selectedDiv).style.display="inline";
	}
	
	selectedDiv=$block;
	
}