Errror message after Pre-installation check

[cc1452]

Uploaded Elxis and started running installation.
Step 1 Pre-installation check showed all writable.
When I click "Continue" I get error message:

Forbidden
You don't have permission to access /elxis/installation/index.php on this server.
Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.

What could be reason? Do I need to change file permissions? If yes: what CMOD?

Thanks.

[Ivan Trebješanin]

Most probably your apache is installed as mod_php, which would probably need following:

Readable for owner:
Files: 644
Folders: 755

Writeable by owner:
Files: 666
Folders: 777