In this post we will discuss about one way to resolve issue which sometimes we got while opening SharePoint 2013 site in SharePoint 2013 designer. The error comes as:
The folder name is not valid. See fig for ref.
Also you can check:
I have tried the below solution and it worked fine for me. But not sure if the same thing will resolve in all other cases also.
First I was opening using http URL, it was not opening.
When I opened the site using https URL, it worked for me.
Hope this will be helpful.