title: Get sum of margin and height with jQuery
body: <p>I want to get the sum of <code>margin-top</code> size and <code>height</code> of another layer.</p>
  
  <p>the margin-top of <code>.nav1</code> is 30px and the height of <code>.main</code> is 28px</p>
  
  <p>I use this code:</p>
  
  <pre><code>$('.nav').css('margin-top').replace('px', '') + $('.main').outerHeight()
  </code></pre>
  
  <p>but the result of my sum is <code>3028</code></p>
  
  <p>How can I calculate the sum of these two numbers?</p>