function checkForm (emailForm){
var emailSender = false;
var emailRecipient = false;
var formValid = true;
emailRecipient = IsEmailValid (emailForm.recipient.value);
emailSender = IsEmailValid (emailForm.senderemail.value);
if (emailForm.sendername.value == ""){
	alert("please enter your name"); 
	formValid=false;
}

//Check Recipient's E-mail

else if (emailRecipient == false){
	alert("Invalid Friend's E-mail");
	formValid=false;
}

//Check Sender's E-mail

else if (emailSender == false){
	alert("Invalid Sender E-mail"); 
	formValid=false;
}

return formValid;



}




function IsEmailValid(checkThisEmail)
{
var myEMailIsValid = true;
var myAtSymbolAt = checkThisEmail.indexOf('@');
var myLastDotAt = checkThisEmail.lastIndexOf('.');
var mySpaceAt = checkThisEmail.indexOf(' ');
var myLength = checkThisEmail.length;


// at least one @ must be present and not before position 2
// @yellow.com : NOT valid
// x@yellow.com : VALID

if (myAtSymbolAt < 1 ) 
{myEMailIsValid = false}


// at least one . (dot) afer the @ is required
// x@yellow : NOT valid
// x.y@yellow : NOT valid
// x@yellow.org : VALID

if (myLastDotAt < myAtSymbolAt) 
{myEMailIsValid = false}

// at least two characters [com, uk, fr, ...] must occur after the last . (dot)
// x.y@yellow. : NOT valid
// x.y@yellow.a : NOT valid
// x.y@yellow.ca : VALID

if (myLength - myLastDotAt <= 2) 
{myEMailIsValid = false}


// no empty space " " is permitted (one may trim the email)
// x.y@yell ow.com : NOT valid

if (mySpaceAt != -1) 
{myEMailIsValid = false}


if (myEMailIsValid == true)
{return true}
else
{return false}
}