When attempting to add a summary links web part, you may receive the following 0x80070002 error:
Unable to add selected web part(s). Could not load XSL file. The system cannot find the file specified. (Exception from HRESULT: 0x80070002)
There are a few possible solutions to this problem. Let's start with the simplest!
NOTE: The information provided below relates to the SharePoint 2010 web interface.
Publishing features must be enabled at the site collection and site level for the summary links web part to work.
For the site collection, navigate to Site Actions>Site Settings > Site Collection Administration > Site collection features. If you are in a subsite of the site collection the navigation path will be Site Actions > Site Settings > Site Collection Administration > Go to top level site settings > Site Collection Administration > Site collection features. Locate SharePoint Server Publishing Infrastructure and click "Activate". If the button reads "Deactivate", then the publishing infrastructure has already been activated and you can skip this step.
At the site level, navigate to Site Actions > Site Settings > Site Actions > Manage site features. Locate SharePoint Server Publishing and click "Activate". If the button reads "Deactivate", then the publishing infrastructure has already been activated and you can skip this step.
If publishing features were already enabled or the problem persists, read on!
It could be that the XSL file that the summary links web part requires is checked out. From the root of your site collection navigate to Site Actions > View All Site Content > Document Libraries > Style Library > XSL Style Sheets. You *should* find a document named ItemStyle.xsl which will show without the .xsl extension as simply "ItemStyle". If you do not see this file, select Library > Library Settings from the ribbon then Permissions and Management > Manage files which have no checked in version. If you see ItemStyle.xsl in the Files checked out to others section, click the checkbox to select the ItemStyle.xsl file, then click the Take Ownership of Selection link at the top of the page. The file should shift to the Files checked out to me section. Next, click the location link to go back to the XSL Style Sheets library. Once there, highlight the ItemStyle file and choose Check In from the drop down. From the Check in dialog, select the major version (publish) option, ensure Retain Check Out is set to No and click OK.
If the problem persists, we've got one more thing to try.
One last possibility is to copy the ItemStyle.xsl file from a different site collection. From the root of a different site collection navigate to Site Actions > View All Site Content > Document Libraries > Style Library > XSL Style Sheets. Once you find a site collection that contains the ItemStyle.xsl file, hover over the file and select Send To > Download a Copy then save the document to your computer. Navigate to the same location in the problematic site collection, click Add document and upload the ItemStyle.xsl file.
