Michael:

Script Installed successfully but after installation when a link is been clicked including login/signup link it shows Internal Server Error

The server encountered an internal error or misconfiguration and was unable 
to complete your request.

below is my .htaccess setting:

AddType video/mp4 .mp4

#Options -MultiViews

#Options -Indexes

## Uncomment (remove # ONLY NOT ##) line below if installed in folder and add folder name after / ## Example: Script is installed in /public_html/folder/ then it should be: Rewritebase /folder/ ## Then the files below should be (add slash to all): /index.php?action=$1 ## Uncomment the code below to Use PHP 5.4 # AddHandler application/x-httpd-php54 .php

RewriteEngine On

## Uncomment the following line to use the multi-domain feature
# RewriteCond %{HTTP_HOST} ^yourseconddomain\.com$ [NC]
# RewriteRule ^(.*)$ http://ift.tt/1EsralK [R=301,L]

#Rewritebase /
## Admin Panel
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^admin/(.*)?$ admin/index.php?a=$1 [QSA,NC,L]

## Application Handler
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^(.*)?$ index.php?a=$1  [QSA,NC,L]

Error 404

ErrorDocument 404 /index.php?a=404

NOTE: I don't have access to apache my website is installed on 1and1.com