function isValidEmail(str) 
{

  // are regular expressions supported?
  var supported = 0;
  if (window.RegExp) 
  {
    var tempStr = "a";
    var tempReg = new RegExp(tempStr);
    if (tempReg.test(tempStr)) 
	 {
		 supported = 1;
	 }
  }

  if (!supported)
  {
    return (str.indexOf(".") > 2) && (str.indexOf("@") > 0);
  }
  
  var r1 = new RegExp("(@.*@)|(\\.\\.)|(@\\.)|(^\\.)");
  var r2 = new RegExp("^.+\\@(\\[?)[a-zA-Z0-9\\-\\.]+\\.([a-zA-Z]{2,3}|[0-9]{1,3})(\\]?)$");
  return (!r1.test(str) && r2.test(str));
}