title: a simple line with css doesn't appears sometimes on chrome
body: <p>I don't understand because sometimes a simple color line doesn't appears with Chrome.
  My line is defined with CSS code :</p>
  
  <pre><code>/* line warning */
  .line_warning {
  background-color:#ff9900; 
  color:white; 
  margin-top:5px; 
  margin-bottom:5px; 
  height: 1px;
  }
  </code></pre>
  
  <p>Apparently, I have this problem only with chrome (I use Bootstrap).</p>
  
  <p>Thank you in advance if you have any idea to resolve it.</p>