"Could not open Design view. Quote values differently inside a '<% ..."value"...%>' block."

 "Could not open Design view. Quote values differently inside a '<% ..."value"...%>' block."

It's a bug in the visual studio .net.

if you have a something like this: <a href="<%#pageVariables("basePath")%>index.aspx">, now you are not able switch back to design view.

The solution is: Replace the "double quote" of html attribute with "single quote"

From: <a href="<%#pageVariables("basePath")%>index.aspx">

To: <a href='<%#pageVariables("basePath")%>index.aspx'>