So you’ve set up your complex managed meta data structure, added all your termsets and terms and everything is looking mighty fine! You create a document library with the managed metadata column, add some documents and tag them with values from your metadata store.

The only thing missing now is the meta data navigation menu that allows you to take advantage of this (pretty nice) Sharepoint 2010 feature.

You’re supposed to be able to configure it through the Metadata navigation settings link under General settings in the document library settings:

But it’s not there. Chances are you’ve forgotten to activate the feature that allows using the metadata filter feature; go to Site Settings – Manage Site Features and activate “Metadata Navigation and Filtering”:

When attempting to add a taxonomy field control to your custom page layout, it will automatically be given a tag looking something similar to this:

<CustomTag_0:TaxonomyFieldControl FieldName="81d247d1-0373-4a2d-9e81-d4b69bf3e091" runat="server"></CustomTag_0:TaxonomyFieldControl>

When attempting to render this in Sharepoint Designer you’ll be told that “TagPrefix is not registered in this Web Form”:

If you’re one of those painfully optimistic characters you’ll still attempt to run it in the browser, which gives you the  ASP.NET error screen with the following message:

“Parser Error Message: Unknown server tag ‘CustomTag_0:TaxonomyFieldControl”

For those who wants to dig even deeper than this, the following error message appears in the application event log:

The solution is simple: just add a reference to the assembly which contains the Taxonomy Picker control at the top of your Page Layout:

<%@ Register Tagprefix="Taxonomy" Namespace="Microsoft.SharePoint.Taxonomy" Assembly="Microsoft.SharePoint.Taxonomy, Version=14.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c" %>

Then change the <CustomTag_0:TaxonomyFieldControl> to <Taxonomy:TaxonomyFieldControl> and off you go (remember there is a closing tag too, by the way..):

<Taxonomy:TaxonomyFieldControl FieldName="81d247d1-0373-4a2d-9e81-d4b69bf3e091" runat="server"></Taxonomy:TaxonomyFieldControl>