title: opacity filter not working in firefox
body: <p>I'm new to html and css/jquery. still i managed to create a website on my own using chrome's inspect element and other sources. But, the opacity filter is not working in firefox (version of firefox im using is 20.0.1). 
  For the section "myHobbie" all the images are using the opacity factor (<code>-webkit-filter:opacity = 50%</code>) but when it comes to firefox, i found that it does not support webkit.</p>
  
  <p>Can anyone please give me any other alternative for this so that it works for both firefox and chrome? Also if possible, for IE too.</p>
  
  <p>My website url is: <code>www.srikarshastry.com/index_vertical.html</code></p>
  
  <p>Thank you in advance.</p>