Those of you that have delved into the customization of WCM capable sites and page layouts may have noticed that when you drag a content control on to the page and view it in the browser you get an “Unspecified Error” – Gee thanks, that was informative.
Luckily there is (at least in some cases) a fairly easy explanation:
When you drag a content control on to your page layout the it is likely prefixed with CMSC (I assume this stands for content management server control). This prefix is not registered at the top of your page so you have two options (that I know of).
Search and replace CMSC with PublishingWebConrols (which is registerd), or copy/paste the entire “register” line for Tagprefix=”PublishingWebControls” and replace PublishingWebControls with CMSC.
I hope this helps,