Problème HTTP Error 500 avec site joomla

Bonjour,

Je viens d'installer mon premier site Joomla avec VirtueMart sur un serveur..
Suite à l'installation, il y a des messages d'erreurs qui s'affiche en bas des pages:
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HTTP Error 500 Internal server error
Introduction

The Web server (running the Web Site) encountered an unexpected condition that prevented it from fulfilling the request by the client (e.g. your Web browser or our CheckUpDown robot) for access to the requested URL.

This is a 'catch-all' error generated by the Web server. Basically something has gone wrong, but the server can not be more specific about the error condition in its response to the client. In addition to the 500 error notified back to the client, the Web server should generate some kind of internal error log which gives more details of what went wrong. It is up to the operators of the Web server site to locate and analyse these logs.

500 errors in the HTTP cycle

Any client (e.g. your Web browser or our CheckUpDown robot) goes through the following cycle when it communicates with the Web server:

Obtain an IP address from the IP name of the site (the site URL without the leading 'http://'). This lookup (conversion of IP name to IP address) is provided by domain name servers (DNSs).
Open an IP socket connection to that IP address.
Write an HTTP data stream through that socket.
Receive an HTTP data stream back from the Web server in response. This data stream contains status codes whose values are determined by the HTTP protocol. Parse this data stream for status codes and other useful information.
This error occurs in the final step above when the client receives an HTTP status code that it recognises as '500'.

Fixing 500 errors - general

This error can only be resolved by fixes to the Web server software. It is not a client-side problem. It is up to the operators of the Web server site to locate and analyse the logs which should give further information about the error.

Fixing 500 errors - CheckUpDown

Please contact us (email preferred) whenever you encounter 500 errors on your CheckUpDown account. We then have to liaise with your ISP and the vendor of the Web server software so they can trace the exact reason for the error. Correcting the error may require recoding program logic for the Web server software, which could take some time.
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Sachant qu'en travaillant en local avec easyphp, j'ai jamais eu ce problème, pouvez vous me dire de quoi il s'agit et comment le résoudre..
Merci à tous..