CSS – Expanding Underlines

The other day I was visiting Grid Style Sheets and was fascinated by the fact that the underlines of the links seemed to expand on mouse over. At first I tried simply using transition in conjunction with margin and padding but unfortunately the results were a bit shaky. Therefore I decided to actually examine the code and found they were using the ::before pseudo-selector. After some tinkering around, I landed on this solution for a simplified version of expanding lines for all links:

a:link, a:visited {
  color: #66F;
  text-decoration: none;
  position: relative;
  transition: all 1s;
}
a:hover {
  color: #00F;
}
a:link::before, a:visited::before {
  background: #DDF;
  box-shadow: 0 0 1px #00F;
  content: '';
  height: 2px;
  position: absolute;
  top: 100%;
  transition: all 1s;
  width: 80%;
  margin-left: 10%;
}
a:hover::before {
  background: #33F;
  box-shadow: 0 2px 2px #CCF;
  width: 110%;
  margin-left: -5%;
}

Here is how the end result looks (try moving your mouse over either Google or Bing:

Expanding Underlines

Pretty cool, right?! CSS3 Definitely adds some cool style to the web these days. 😎