>My problem was that I was referencing the CSS file with tilde; as "~\Content\Bootstrap.....css" When I removed the tilde and made it "\Content\Bootstrap... css" all began to work.

The tilde should work in Razor pages to auto-translate. But your path separators need to be forward slashes, not backward slashes.

+++ Rick ---

>
>Thank you.
>
>>You're probably missing the Bootstrap script file reference. Make sure you add the CSS *AND* the .js file to your page.
>>
>>All components that require actions like clicks tend to be logic fired through script that lives in the Bootstrap.js file.
>>
>>+++ Rick ---
>>
>>>I have a strange situation. I found a Fiddle that has an example of Bootstrap 3 Collapse menu. The menu that collapses into a button when the browser gets to the mobile size. And then by clicking on the button the menu is opened. When I run this code in the Fiddle, it works. This is the Fiddle:
>>>
>>>http://jsfiddle.net/9pruK/
>>>
>>>But when I created a test.html with exactly the code from this fiddle it does not work. That is, in my test.html the button is created but clicking on the button does not produce the menu. I have compared the Bootstrap.css in the Fiddle and the one I use and it is the same (the size is exactly the same). What can be causing my test.html not to work?
>>>
>>>TIA