Cause : This error is encountered when default page of your website is not set.
Resolution :
1. Add your default page name in your web.config file.
2. Set default page from your Control Panel options available in this knowledgebase section.
3. Set default page from IIS.
Log into your server via remote desktop connection.
Click Start – RUN – Type inetmgr and press enter key.
Expand IIS – Click on sites – Click on your website.
Click on default document option – Click on add.
Here you can set your default page name.