title: Modify Application.Master in Sharepoint 2007
body: <p>I need to deploy a Silverlight navigation on my /_layouts/ pages on a Sharepoint site.  From what I understand, this requires editing the site's Application.master. However, when I edit it and deploy(after reseting IIS) I get the following error: <br /><br /></p>
  <blockquote>
  Type 'System.Web.UI.WebControls.ContentPlaceHolder' does not have a public property named '__Error'.   at System.Web.UI.ControlBuilder.AddProperty(String filter, String name, String value, Boolean mainDirectiveMode) 
     at System.Web.UI.ControlBuilder.PreprocessAttributes(ParsedAttributeCollection attribs) 
     at System.Web.UI.ControlBuilder.Init(TemplateParser parser, ControlBuilder parentBuilder, Type type, String tagName, String id, IDictionary attribs) 
     at System.Web.UI.WebControls.ContentPlaceHolderBuilder.Init(TemplateParser parser, ControlBuilder parentBuilder, Type type, String tagName, String ID, IDictionary attribs) 
     at System.Web.UI.ControlBuilder.CreateBuilderFromType(TemplateParser parser, ControlBuilder parentBuilder, Type type, String tagName, String id, IDictionary attribs, Int32 line, String sourceFileName) 
     at System.Web.UI.ControlBuilder.CreateChildBuilder(String filter, String tagName, IDictionary attribs, TemplateParser parser, ControlBuilder parentBuilder, String id, Int32 line, VirtualPath virtualPath, Type& childType, Boolean defaultProperty) 
     at System.Web.UI.TemplateParser.ProcessBeginTag(Match match, String inputText) 
     at System.Web.UI.TemplateParser.ParseStringInternal(String text, Encoding fileEncoding) 
  </blockquote>
  <p>Does anyone have any insight into this error?</p>