function isEmail(s) {
        if (s=="") return false;
        if(s.indexOf(" ")>0) return false;
        var i = 1;
        var sLength = s.length;
        if (s.indexOf(".")==sLength) return false;
        if (s.indexOf(".")<=0) return false;
        if (s.indexOf("@")!=s.lastIndexOf("@")) return false;
        while ((i < sLength) && (s.charAt(i) != "@"))  { i++  }
        if ((i >= sLength) || (s.charAt(i) != "@")) return false;
        else i += 2;
        while ((i < sLength) && (s.charAt(i) != "."))  { i++  }
        if ((i >= sLength - 1) || (s.charAt(i) != ".")) return false;
     	var str="1234567890abcdefghikjlmnopqrstuvwxyzABCDEFGHIKJLMNOPQRSTUVWXYZ-@._";
        for(var j=0;j<s.length;j++)
                if(str.indexOf(s.charAt(j))==-1)
                        return false;
        return true;
}

function checkform(){

      if (document.newsletter.email.value=="") {
                        alert("Please enter Your own Email Address!");
                        document.newsletter.email.focus();
                        return false;
                }
	  if (!isEmail(document.newsletter.email.value)) {
                        alert("Invalid Email, Please enter Your own Email again!");
                        document.newsletter.email.focus();
                        return false;
             
                } 
		
                return true;
        }