An error occurred during the compilation of the requested file, or one of its dependencies. The type or namespace name 'Publishing' does not exist

As simple as this error sounds - "An error occurred during the compilation of the requested file, or one of its dependencies. The type or namespace name 'Publishing' does not exist in the namespace 'Microsoft.SharePoint' (are you missing an assembly reference?)", it can be tricky to solve.

The easiest solution I have found to solve is to include the following snippet below your includes in your master page.

<%@ Register Tagprefix="PublishingWebControls" Namespace="Microsoft.SharePoint.Publishing.WebControls" Assembly="Microsoft.SharePoint.Publishing, Version=12.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c" %>

<%@ Register Tagprefix="PublishingNavigation" Namespace="Microsoft.SharePoint.Publishing.Navigation" Assembly="Microsoft.SharePoint.Publishing, Version=12.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c" %>

<%@ Register TagPrefix="PublishingVariations" TagName="VariationsLabelMenu" src="~/_controltemplates/VariationsLabelMenu.ascx" %>
<%@ Register Tagprefix="PublishingConsole" TagName="Console" src="~/_controltemplates/PublishingConsole.ascx" %>

<%@ Register TagPrefix="PublishingSiteAction" TagName="SiteActionMenu" src="~/_controltemplates/PublishingActionMenu.ascx" %></strong>