title: Reference to browser-specific CSS?
body: <p>I'm looking for a reference for browser specific CSS. <br>
  All the things that start with -moz, -webkit, -o, -khtml <br><br></p>
  
  <p>In <a href="https://stackoverflow.com/questions/826782/css-rule-to-disable-text-selection-highlighting">this question</a> for instance, the person answers with all the user-select <br>
  codes for all the browser, but how did he know that Opera has that option? <br>
  I couldn't find documentation for those.</p>