How do I make an ad hover on page?

I'm talking about some of those websites with "Twitter" or "Feedback" hovering near the scroll bar or on the bottom of a page. I understand that it's a type of CSS but unsure 开发者_JAVA百科about which.

Thanks in advance for your help!

.something {
  background-color: #ccc;
  width: 40px;
  height: 40px;
  overflow: hidden;
  position: fixed;
  bottom:10px;
  right: 10px;
  margin: 0px;
  padding: 0px;
}

PS: Get firefox and firebug.

You can right-click anything you see and look at the css for it right there. http://getfirebug.com

You need position: fixed and bottom: 0.
position: fixed will fix it in the viewport, regardless of the scrollbar.