// JavaScript Document


function Validate_String(string, return_invalid_chars)
	 {
	 valid_chars = '1234567890-_.abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';
	 invalid_chars = '';
	 
	 if(string == null || string == '')
		return(true);
	 
	 //For every character on the string.   
	 for(index = 0; index < string.length; index++)
		{
		char = string.substr(index, 1);                        
		
		//Is it a valid character?
		if(valid_chars.indexOf(char) == -1)
		  {
		  //If not, is it already on the list of invalid characters?
		  if(invalid_chars.indexOf(char) == -1)
			{
			//If it's not, add it.
			if(invalid_chars == '')
			   invalid_chars += char;
			else
			   invalid_chars += ', ' + char;
			}
		  }
		}                     
		
	 //If the string does not contain invalid characters, the function will return true.
	 //If it does, it will either return false or a list of the invalid characters used
	 //in the string, depending on the value of the second parameter.
	 if(return_invalid_chars == true && invalid_chars != '')
	   {
	   last_comma = invalid_chars.lastIndexOf(',');
	   
	   if(last_comma != -1)
		  invalid_chars = invalid_chars.substr(0, $last_comma) + 
		  ' and ' + invalid_chars.substr(last_comma + 1, invalid_chars.length);
				  
	   return(invalid_chars);
	   }
	 else
	   return(invalid_chars == ''); 
	 }


function Validate_Email_Address(email_address)
         {
         //Assumes that valid email addresses consist of user_name@domain.tld
         at = email_address.indexOf('@');
         dot = email_address.indexOf('.');
         
         if(at == -1 || 
            dot == -1 || 
            //dot <= at + 1 ||
			dot == at - 1 ||
            dot == 0 || 
            dot == email_address.length - 1)
            return(false);
            
         user_name = email_address.substr(0, at);
         domain_name = email_address.substr(at + 1, email_address.length);                  
         
         if(Validate_String(user_name) == false || 
            Validate_String(domain_name) == false)
            return(false);                     
         
         return(true);
         }