We have a sharepoint 2013 running utilizing document set homepages as core part of our site.

For example, we have CSWPs on this site which display related items and recommendations under the "normal" document set web parts.

Now we want to adapt the layout to make it more pretty, and we are editing the home page via Sharepoint Designer. The correspoding files are in the _cts folder and usually named docsethomepage.aspx

Since we are changing the template, we are editing in "Advanced Mode", but whenever we save the page, all Content Search Web Parts are broken with an error of

Web Part Error: Unknown server tag. Correlation ID: 93fda89c-d4c0-b0dd-3895-84e9d6acc991.

How can we prevent this from happening? What is the reason that these web parts get broken by Sharepoint Designer?

  • what are editing in that file?
    – Mike
    Jul 28, 2014 at 17:28
  • Just replacing the horizontal in the web part zone with vertical or vice versa. Jul 28, 2014 at 21:10
  • Can you edit the page in the browser, without using SharePoint Designer? I think some of those pages are templates that you can't change.
    – Mike
    Jul 29, 2014 at 0:17
  • It is a page template that has web part zones, and anything within those zones I can change in the browser, but the way the template works I cannot change in the browser, just in Sharepoint Designer Jul 29, 2014 at 9:37

2 Answers 2


For some reason SharePoint Designer changes the tags of those web parts EVERY TIME you open it:


needs to be changed back to


and the closing tags in the same way.

I just don't get how I can prevent this from happening!


This was very helpful in figuring this out. In my pages the tag was actually WpNs0 not WpNs1 but I had success changing the

<%@ Register TagPrefix="WpNs0"

tag to instead match what SharePoint Designer puts in:

<%@ Register TagPrefix="spsswc"

Hope this helps someone -- what a nightmare SharePoint Designer is -- not tested much before release, and apparently there are no bug fixes either.

Note - this was tested with Office 365 results may be different on-prem

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