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Creating custom error handling pages

You can configure the system to display custom pages instead of standard error messages. Custom pages help reduce the inconvenience caused to visitors if they run into an error while browsing your website, and also improves the security of the site by hiding potentially sensitive internal data (such as code in stack traces). You can create custom pages for this purpose with any kind of content, such as an apology or additional instructions, and then configure the system to display the pages in the appropriate situations.

Adding custom Page not found error pages

The Page not found error (404 HTTP status code) is one of the most common problems encountered by visitors. Kentico provides several features that allow you to conveniently set up a custom page as a response. For page not found errors, the error page can either be a physical .aspx file placed under the web project or a dedicated page created in a specific website's content tree.

To assign your custom page to a particular website (or globally):

  1. Go to Settings -> Content.
  2. Enter the URL of the given page as the value of the Page not found URL setting, for example: ~/SpecialPages/PageNotFound.aspx

    Since there are two possible types of error pages, the system interprets the URL in two different ways. The sample URL value above specifies either:

    • The URL of a physical page named PageNotFound.aspx located in the web project under a folder called SpecialPages.
    • If such a file does not exist, the system attempts to select a Kentico page under the current website, with an alias path equal to /SpecialPages/PageNotFound.
  3. Click Save.

It is recommended to use Kentico pages for page not found error pages. With this approach, you can define the error page's content using the portal engine and leverage all of its features. For instance, you can translate the page not found page on a multilingual website and Kentico automatically displays the culture version that matches the language selected by the user.

You do not need to manually handle the HTTP response code of the page specified by the setting. The page automatically returns a 404 status code when accessed (applies to both pages and physical pages). This allows applications, services and web crawlers to find out that a page not found error has occurred.

Handling 404 errors for general content

To ensure that the system returns your custom Page not found error page for invalid requests that target all types of site content, not just the pages processed by the Kentico engine, you need to fulfill several additional requirements:

  • The site must be hosted on IIS version 7 or newer.
  • The Managed pipeline mode of the application pool needs to be set to Integrated.

If your environment meets the conditions above:

  1. Edit your application's web.config file.
  2. Find the system.webServer section directly under the root (i.e. not under a specific <location> element).
  3. Add the following attribute to the section's <modules> element:
<modules runAllManagedModulesForAllRequests="true">
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Handling general errors

Kentico is a standard ASP.NET application, so you can configure the handling of all types of errors and exceptions via the <customErrors> element under the <system.web> section of your web.config file. See the customErrors MSDN article for more information.

To use custom error handling pages, you need to set the mode attribute of the <customErrors> element to RemoteOnly (recommended) or On.

You can add any number of child <error> elements representing individual types of HTTP errors that you wish to handle.

  • You need to enter the HTTP response code of the given error into the statusCode attribute and the URL of the appropriate error page as the redirect value.
  • It is recommended to add general error pages directly into your web project as .aspx files, for example under the CMSMessages folder.
  • You can define the content of the error page to match your specific requirements.
  • Keep in mind that your custom error pages should always return the appropriate HTTPResponse status code.
	<customErrors defaultRedirect="~/CMSMessages/Error.aspx" mode="RemoteOnly">
		<error statusCode="500" redirect="~/CMSMessages/CustomError.aspx" />
		<error statusCode="503" redirect="~/CMSMessages/CustomError.aspx" />

When using <customErrors>, it is also recommended to disable handling of errors on the level of IIS by adding a httpErrors element under the application's main <system.webServer> element, with the existingResponse attribute set to PassThrough:

	<httpErrors existingResponse="PassThrough" />

Before deployment

Set custom error messages as described in this procedure before deploying your website and going live. Also, remember to disable debugging and tracing for your ASP.NET application.

Using <httpErrors> for error handling

Alternatively, handling of errors can also be configured on the IIS level via the <httpErrors element under your web.config's main <system.webServer> element. See the HTTP Errors article for more information.

Choose and test which approach works best, depending on the environment in which your application is running.

Page not found error conflicts

If you have the defaultRedirect attribute of the customErrors element set in your web.config file, the default redirect may override the page assigned for 404 page not found errors in the Kentico settings. This applies to URLs ending with the .ashx, .asmx or .svc extensions.

To work around this behavior, you can set the redirectMode attribute to ResponseRewrite:

<customErrors defaultRedirect="~/CMSMessages/CustomError.aspx" mode="RemoteOnly" redirectMode="ResponseRewrite">