Overview

This article addresses an issue where content, e.g., text, graphics, URLs, and scripts, are not displayed when visiting a website, and GFI WebMonitor is blocking them instead of allowing them.

Root Cause

CDNs (Content Delivery Network, sometimes also called Content Distribution Networks) are used to distribute or deliver content across the web. In a normal web host, all files are stored centrally on a web server and delivered on demand. Hence, the site's load-time dramatically depends upon the capability of that server.

A CDN system keeps the copies of files at different servers across a global network. These networks are made up of several dedicated servers, which work as distributed hosts of the content, especially for static files, e.g., videos, Java scripts, CSS files, etc.

Users are provided with the content from the servers located at their nearest/fastest point of presence. The host selection is based on the user's IP address. If the CDN server is blocked, some of the website content will not be displayed (icons, images, etc.) or executed (scripts) correctly.

Resolution

There are two possible resolutions for this issue:

1. To discover the sources, look in the lower left-hand corner of your browser for a caution sign. Double-click it, and it will open a list of rendering errors on the page. In the list of errors, you will see the URLs that are linked to the errors.
   
   After you identify the location of these images, and if the website is trusted, add them as Site entries in the WebMonitor console under Settings > Policies > Whitelist.
   
   
2. Make sure that the 'CDNs' category is not blocked by one of the Web Filtering policies.
   
   
   1. From the WebMonitor console, navigate to Settings > Policies.
   2. Edit all the affected policies and make sure that General Interest > CDNs is not blocked.