/**
 * generate random string
 * @author	Paul Kruijt
 * @param	integer	str_length
 * @return	string	random_string
 */
function generateRandomString(str_length)
{
	var chars			= '0123456789ABCDEFGHIJKLMNOPQRSTUVWXTZabcdefghiklmnopqrstuvwxyz';
	var str_length		= !str_length ? 10 : str_length;
	var random_string	= '';
	
	for (var i=0; i<str_length; i++)
	{
		var rnum		 = Math.floor(Math.random() * chars.length);
		random_string	+= chars.substring(rnum, rnum+1);
	}
	
	return random_string;
}