Can you help with these error messages?

After installing the cart, I am able to get to the admin panel, but UNABLE to get to the store. Here are the errors I receive :huh: :

Warning: main(./extension.inc): failed to open stream: No such file or directory in /.../web/catalog/index.php on line 25

Warning: main(): Failed opening './extension.inc' for inclusion (include_path='.:/usr/local/php/include') in /.../web/catalog/index.php on line 25

Warning: main(./common.): failed to open stream: No such file or directory in /.../web/catalog/index.php on line 26

Warning: main(): Failed opening './common.' for inclusion (include_path='.:/usr/local/php/include') in /.../web/catalog/index.php on line 26

Fatal error: Call to undefined function: session_pagestart() in /.../web/catalog/index.php on line 31

Thanks a bunch for the help. Any assistance is greatly appreciated.

try reuploading all of the files.

Thank you:D