title: Are modern jquery selectors backwards compatible?
body: <p>So I know how to use javascript, and have just started trying to learn jquery. When you select an element with <code>$('css-selecor')</code>, I'm just wondering about which selectors can be used. I want to use something like <code>:nth-child(n)</code>, which is a CSS3 selector. Now my question is, does the user's browser have to be compatible with CSS3 for that to work, or is jquery built to use those selectors to locate the element regardless of the browser? </p>
  
  <p>I am using jquery 1.9.1</p>