403 Error- Forbidden! on form submit

Hey guys I need help here, I receive a 403 Error- Forbidden! each time a form is submitted, I have a.php submitting a form to b.php however b.php throws "403 forbidden You are not permitted to access the requested URL" However if accessing the file (b.php) through the browser directly without submitting the form it loads perfectly it only happens on form submit, both files are owned by the group administrator, both are under the same folder ... any ideas would be helpful

 

thanks till for your reply. I forgot to update this thread, it turned out to be mod security blocking post as it was a chain rule

thanks

 

Joomla giving ISPConfig errors

I transferred a Joomla website from another ISP and when it went live on my server, I had all the images on the forum not visible on the forum. I then went and had a look at the permissions and ownerships of the files and folders, and they are fine. I keep getting the error:

403 Error- Forbidden!

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The following error occurred:

You are not permitted to access the requested URL
Please contact the Webmaster with any queries.

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powered by ISPConfig

Any ideas on how to fix this problem would be appreciated