Manage error handling page templates in Optimizely <<product-name>>'s Content Management System (CMS) to provide contextual help or links to existing content when website errors occur. <<product-name>> provides three standard error handling pages:
403: Unauthorized Access: The user does not have permission to view the requested file or resource.
404: Page Not Found: The page or file cannot be found or does not exist.
500: Unhandled Error (aka HTTP 500 error): Generic error suggesting a problem with the website's server.
Use the steps below to customize these pages:
To customize a page, sign in to the Admin Console as an **ISC_ContentEditor** or **ISC_ContentAdmin**, then access the website using **View Websites**.
Select **Show CMS** in the upper left corner of the screen, then select **Show CMS**.
Select **Content Tree** in the upper left corner to expand the Content Tree.
Select **Edit** .
Select the expand arrow to the left of **Home** to expose the section.
Select the expand arrow to the left of **Unhandled Error** to expose the section.
Select a page: **Unhandled Error**, **Page Not Found** or **Unauthorized Access**.
Click **Edit this Page** in the upper right corner.
Enter the desired content into the appropriate field. For instance, the **Page Title** could be updated from **Page Not Found** to **Page No Longer Exists**.
Scroll down and click **Save**. The edited page in the Content Tree will appear orange until it is published.
If a widget is modified on a page, an orange box surrounds the widget until it is published. Some modifications update the widget, but don't require the widget to be published; for example, if the **Page Information** and **Page Title** are modified. the widget automatically inherits that edit.
If you are an **ISC_ContentApprover** or **ISC_ContentAdmin**, click **Publish** in the upper right corner to approve the new content and publish it to the website.
## Troubleshoot error handling
If the Application's error handling pages are not returning correctly for the expected events, or if users are seeing the generic IIS error page, the **web.config** file may not be set up correctly. The example below shows the proper mapping to ensure the correct page returns: