function echeck(str) 
{
	var at = "@";
	var dot = ".";
	var lat=str.indexOf(at);
	var lstr=str.length;
	var ldot=str.indexOf(dot);
	if (str.indexOf(at)==-1) {
		alert("Invalid Email Address");
		return false;
	}
	if (str.indexOf(at)==-1 || str.indexOf(at)==0 || str.indexOf(at)==lstr){
		alert("Invalid Email Address");
		return false;
	}
	if (str.indexOf(dot)==-1 || str.indexOf(dot)==0 || str.indexOf(dot)==lstr){
		alert("Invalid Email Address");
		return false;
	}
	 if (str.indexOf(at,(lat+1))!=-1){
		alert("Invalid Email Address");
		return false;
	}
	if (str.substring(lat-1,lat)==dot || str.substring(lat+1,lat+2)==dot){
		alert("Invalid Email Address");
		return false;
	}
	if (str.indexOf(dot,(lat+2))==-1){
		alert("Invalid Email Address");
		return false;
	}
	if (str.indexOf(" ")!=-1){
		alert("Invalid Email Address");
		return false;
	}
	return true;
}

function checkval()
{
            
	if(document.advForm.visitor.value=="")
	{
		alert("Visitor name could not be left Blank");
		document.advForm.visitor.focus();
		return false;
	}
	if(document.advForm.visitormail.value=="")
	{
		alert("Visitor email Address could not be left Blank");
		document.advForm.visitormail.focus();
		return false;
	}
	if (echeck(document.advForm.visitormail.value)==false)
	{
		document.advForm.visitormail.focus();
		return false;
	}
	
    if(document.advForm.friend.value=="")
	{
		alert("friend name could not be left Blank");
		document.advForm.friend.focus();
		return false;
	}
	if(document.advForm.friendmail.value=="")
	{
		alert("Friend email Address could not be left Blank");
		document.advForm.friendmail.focus();
		return false;
	}
	if (echeck(document.advForm.friendmail.value)==false)
	{
		document.advForm.friendmail.focus();
		return false;
	}      
	
	return true;
}