letter-spacing 「文字の間隔」

<style type="text/css">
.common div{
  font-family   : "メイリオ", sans-serif;
  width         : 290px;
  border        : 2px solid #6495ed;
  background    : #e7e7ff;
  padding       : 10px;
}
div.cssTitle {
  margin-top    : 10px;
  background    : #6495ed;
  color         : #fff;
  font-weight   : bold;
}
.css_letter-spacing_normal{
  letter-spacing : normal;
}
.css_letter-spacing_value1{
  letter-spacing : 10px;
}
.css_letter-spacing_value2{
  letter-spacing : 2em;
}
.css_letter-spacing_value3{
  letter-spacing : -1px;
}

<!-- html -->
<div class="common">

  <div class="cssTitle">letter-spacing : normal;</div>
  <div class="css_letter-spacing_normal">
  CSSの「letter-spacing」は、文字の間隔を指定します。CSS "letter-spacing" specifies character spacing.
  </div>

  <div class="cssTitle">letter-spacing : px;</div>
  <div class="css_letter-spacing_value1">
  CSSの「letter-spacing」は、文字の間隔を指定します。CSS "letter-spacing" specifies character spacing.
  </div>

  <div class="cssTitle">letter-spacing : em;</div>
  <div class="css_letter-spacing_value2">
  CSSの「letter-spacing」は、文字の間隔を指定します。CSS "letter-spacing" specifies character spacing.
  </div>

  <div class="cssTitle">letter-spacing : px;（負の値）</div>
  <div class="css_letter-spacing_value3">
  CSSの「letter-spacing」は、文字の間隔を指定します。CSS "letter-spacing" specifies character spacing.
  </div>

</div>