To test if your php side code works, use the $_GET[] setup in your php script, and add echo mysql_error(); below the mysql query update, and then manually visit your page.
ie open the url in a browser,
http://yoursite/score_send.php?uid=1&score=10
Also, you do a mysql_select_db("dbname", $con) referring to your database name as dbname ... which Im pretty sure is not the actual name of your database.
If you applied the above, the second issue should be displayed in your browser as: error database "dbname" does not exist.