First off, this isn't an error, but a warning. Solution? It's really quite simple, do what the warning suggests🙂
The mysql_db_query() function is deprecated and will be removed from PHP at some point in the future. Use the mysql_select_db() and mysql_query() functions. Do:
mysql_select_db("my_db");
mysql_query("SELECT * FROM my_table");
instead of:
mysql_db_query("my_db", "SELECT * FROM my_table");
-geoff