title: R Bookdown The GitBook toolbar not visibile in IE11 in Minimal Book Example
body: <p>A strange thing is happening browsing a <a href="https://bookdown.org/yihui/bookdown-demo/" rel="noreferrer">A Minimal Book Example</a> with Chrome and Edge shows the GitBook toolbar. However when using internet Explorer 11 with windows 10 the toolbar doesn't show but is working.</p>
  
  <blockquote>
    <p>Versie: 11.98.16299.0<br>
    Updateversies: 11.0.48 (1&lt;84047206)  </p>
  </blockquote>
  
  <p>Initially I thought this is a browser problem till I visited <a href="https://bookdown.org/yihui/bookdown/" rel="noreferrer">bookdown: Authoring Books and Technical Documents with R Markdown</a> and the toolbar was showing using the same IE11 browser. </p>
  
  <p>I expect it is in the _output.yml but can find it, the location f the css could be the root cause.</p>
  
  <pre><code>bookdown::gitbook:  
    highlight: default    
    css: css/style.css  
    config:  
      toc:  
      collapse: section  
      download: null  
      toolbar:  
      position: fixed  
      search: yes  
      sharing:  
        facebook: no  
        twitter: no  
        google: no  
        weibo: no  
        instapper: no  
        vk: no  
        all: []   
  </code></pre>