function validate(f){
	if(f.email.value==""){
		alert("You haven't entered an email address")
		f.email.focus()
		return false
	} else if(!isEmail(f.email.value)){
		alert("You must enter a valid email address")
		f.email.focus()
		return false
	} else {
		return true
	}
}

function isEmail(e) {
	at=e.indexOf('@')
	dot=e.indexOf('.')
	end=e.length
	subone=e.substring(at+1,dot)
	domainbeforedot=subone.length
	subtwo=e.substring(dot+1,end)
	domainafterdot=subtwo.length
	if (e == "") {
		return false
	} else if(e.indexOf ('@',0) == -1 || e.indexOf ('.',0) == -1  || domainbeforedot < 1 || domainafterdot < 2 ) {
		return false
	} else {
		return true
	}
}