I have just started front-end development with Wordpress Twenty Twelve child theme.
I want to make my background full-screen responsive. I followed from this post: Full-screen responsive background image because it is exactly what I'm looking for.
But when I copy and paste this css code into my style.css:
img.bg {
  /* Set rules to fill background */
  min-height: 100%;
  min-width: 1024px;
  /* Set up proportionate scaling */
  width: 100%;
  height: auto;
  /* Set up positioning */
  position: fixed;
  top: 0;
  left: 0;
}
@media screen and (max-width: 1024px) { /* Specific to this particular image */
  img.bg {
    left: 50%;
    margin-left: -512px;   /* 50% */
  }
}
It doesn't work. It feels like img.bg doesn't exist. This is my current website.
Please help! I cannot move on without this and I'm behind schedule :( Thank you for your time!
 
     
     
    