function strEmailValidity(field) 
{
  var strErrMsg = new String("");
	var strField  = new String(field);
  
  if ((strField.length <= 0) || (strField.toLowerCase() == "null") || (strField.toLowerCase() == "undefined"))
  {
    strErrMsg += "Please enter your email address.\n";
  }
  else
  {
	  var intAtIndex      = strField.indexOf("@");
	  var intDotIndex     = strField.indexOf(".");
	  var intLastDotIndex = strField.lastIndexOf(".");

    if ((intAtIndex < 1) || (intAtIndex == (strField.length - 1)) || (intDotIndex < 1) || (intLastDotIndex <= intAtIndex)) 
	  {
	    strErrMsg += "Email address format is invalid.\n";
	  }
	  
    if (strField.indexOf(" ") >= 0)
	  {
	    strErrMsg += "Email address should not contain spaces.\n";
	  }
  }
	
  return strErrMsg;
}