Troubleshooting Tip: Fix slow page loading with a web content filter enabled by whitelisting an advertisement domain

[SassiVeeran]

Description	This article describes how to fix some cases of slow webpage loading by whitelisting the ad-serve domain integrated with the site.
Scope	FortiGate version 6.4 and above. FortiGate version 7.0 and above.
Solution	Sometimes, web pages load slowly when browsing specific websites (asiaone.com will be used as an example in this article). In this example: The website asiaone.com falls under the News and Media category, under the group 'General Interest - Personal', through web filter lookup. The web filter profile enabled in firewall policy and the category has been allowed, so this behavior is unexpected. To resolve the issue, take the following preliminary steps first: Determine whether the website is using any form of advertising. In this case, it was noted that the asiaone.com website queried multiple advertisement domains when the page loaded. Because the advertising category has been blocked in the web filter profile, this slows page loading. Check the web filter logs to verify whether any ad serving URL is being blocked. There are two solutions: Enabling the advertising category can fix the issue, but this is not a recommended configuration for many customer environments. An alternate solution is to whitelist the ad-serving domain integrated with the website. This article explores that option further. To determine the list of domains an advert depends on, install adam:One Assist in the browser as extension. Once the page loads, select the extension button to view the domain list and choose the one ad-serving domain to whitelist. To view the exact domain of the advertisement, use the developer tools built into Chrome: right-click on an advertisement and choose 'Inspect'. This will open a split screen view that shows the web page's information, including the necessary information for this solution: the domain name the advertisement is coming from. After identifying this domain, add it to the web content filter whitelist. Related article: Technical Tip: Using a static URL filter feature to allow/block web sites.