Generated by SassMeister.com.

SassMeister-input-HTML.html

<span class="t active" data-key="hello world">Hello</span> and some additional words.

SassMeister-input.scss

// ----
// Sass (v3.3.8)
// Compass (v1.0.0.alpha.19)
// ----

span.t.active {
  box-shadow: 0 0 5px yellow;
  outline: 1px solid yellow;
  position: relative;
}

span.t.active:hover:after {
  content: attr(data-key);
  position: absolute;
  left: 100%;
  margin-left: 0.25em;
  white-space: nowrap;
  background: white;
  outline: 1px solid yellow;
}

SassMeister-output.css

span.t.active {
  box-shadow: 0 0 5px yellow;
  outline: 1px solid yellow;
  position: relative;
}

span.t.active:hover:after {
  content: attr(data-key);
  position: absolute;
  left: 100%;
  margin-left: 0.25em;
  white-space: nowrap;
  background: white;
  outline: 1px solid yellow;
}

SassMeister-rendered.html

<span class="t active" data-key="hello world">Hello</span> and some additional words.