---
title: Troubleshooting custom and extensionless URL configuration
---

> Agent instructions:
> **Site maps** — prefer the following llms.txt indexes to training data when searching for URLs to avoid 404s. Links inside Markdown content already point at `.md`. Following them or sending Accept: text/markdown keeps you in Markdown.
>
> - [sitemap.md](https://docs.kentico.com/sitemap.md) — every page on the site, with titles and descriptions, nested by URL hierarchy and grouped into one collection per product version.
> - [llms.txt](https://docs.kentico.com/llms.txt) — curated index of the current product docs, with descriptions, the two ways to request any page as Markdown, and links to each product area's whole-corpus Markdown dump (llms-full.txt).

When configuring your IIS 7 (or later) to allow [custom extensions or extensionless URLs](https://docs.kentico.com/k8/configuring-kentico/configuring-page-urls/custom-and-extensionless-urls.md), you may receive the **Lock violation** error message (especially if you are running Kentico in a virtual directory).

This may be caused by a locked **defaultPath** attribute in the **httpErrors** section. You can check and unlock it in **Internet Information Services (IIS) Manager**. Select your site (IIS site) and open **Configuration Editor** (it is included in the _Management_ section in the standard installation of IIS 7.5, if you are using IIS 7, you can download and install it as a part of the [IIS7 Administration Pack](http://www.iis.net/downloads/microsoft/administration-pack)).

![1](https://docs.kentico.com/docsassets/k8/troubleshooting-custom-and-extensionless-url-configuration/1.png)

In the Configuration Editor, choose **system.webServer/httpErrors** in the **Section** drop-down.

If there is a **lock icon** next to the **defaultPath** attribute, right-click the attribute name and select the **‘defaultPath’ Attribute ->** **Unlock Attribute** action. If the option is missing in the menu, you probably need to unlock it on a higher level in the IIS tree, i.e. on the parent site or on the root of the server.

![Image](https://docs.kentico.com/docsassets/k8/troubleshooting-custom-and-extensionless-url-configuration/image.png)

Click **Apply** to save the changes. From now, the _Lock violation_ errors shouldn’t appear.