title: Testing Bootstrap on jsfiddle
body: <p>I'm trying to test some HTML code including bootstrap in jsfiddle, but when including external css references, get this error:</p>
  
  <p><em>For external CSS files use the Resources panel on the left.</em></p>
  
  <p>Those external references are hosted somewhere in an outside server, but apparently it's not called correctly.</p>
  
  <p>How should I call external css references or external javascripts ?</p>
  
  <p><a href="https://i.stack.imgur.com/C2S5e.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/C2S5e.png" alt="enter image description here"></a></p>