Woh, somthing is wrong here wordpress

Hey everyone, ive just put wordpress on my site, im not new to it, but i have learned how to make skins, so i wanted to uses wordpess my self. And now im geting lots of error messages!!

Try to delete a comment and i get ” Forbidden
You don’t have permission to access /wp-admin/admin-ajax.php on this server.

Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.
Apache/1.3.39 Server at jordanparker.co.uk Port 80 “

Try to add a new Categories, Same message.
Try to delete a post, Same message agen.

Has anyone else had this problem ??
Does anyone else know how to solve this problem ??