function checkBackward(){
	var previousSite, matchURL;
	
	if(document.referrer){
		previousSite = document.referrer;
	} else {
		previousSite = null;	
	}
	
	if(previousSite){
		matchURL = previousSite.match("exploringnature");
	}
	
	if(matchURL){
		//do nothing
	} else {
		transformBackLink();
	}
}

function transformBackLink(){
	var elem = document.getElementById("backarrow");
	elem.setAttribute("src", "faded_arrow_back.gif");
	elem.setAttribute("onclick", " ")
}