Configuration error: Unrecognized attribute 'xmlns'

Last Published: April 25, 2020

Error Message

After installing the Web Application Developer Framework (ADF) or Web Applications features of the ArcGIS Server 9.2 for the Microsoft .NET Framework product, running a Web application fails with the error message:

"Configuration Error

Description: An error occurred during the processing of a configuration file required to service this request.
Please review the specific error details below and modify your configuration file appropriately.

Parser Error Message: Unrecognized attribute 'xmlns'. Note that attribute names are case sensitive"


During the installation, unexpected XMLNS attributes were added to the web.config file located under C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\CONFIG.

The presence of the following configuration value at the top of the web.config adds the additional XMLNS attributes upon installation of the Web ADF and Web Applications features:

<configuration xmlns="">

Typically, this error does not occur after installation because on most systems, this line only contains the following value:


Installation of a service pack or patch may also cause this error.

Note that attribute names are case sensitive.

Solution or Workaround

NOTE: The following procedure requires modifying the machine's web.config file. Consult with a qualified computer systems professional, if necessary. ESRI cannot guarantee results from incorrect modifications while following these instructions. Therefore, use caution and proceed at your own risk.

  1. Navigate to C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\Config.
  2. Create a backup copy of the web.config file.
  3. Open the web.config file in a text editor application, such as MS WordPad.
  4. Locate the <httpHandlers> attribute. The three lines that immediately follow the <httpHandlers> line were added by the installation of the Web ADF or Web Application features.
  5. Edit each of these three lines to remove the XMLNS="" attribute. Example follows.

    The end of each line before edit:

    PublicKeyToken=8fc3cc631e44ad86" validate="false" xmlns="" />

    The end of each line after edit:

    PublicKeyToken=8fc3cc631e44ad86" validate="false" />

  6. Save the changes to the web.config file.

Article ID:000009461

  • ArcGIS Server

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