Wide Horizon skin by AO3 

Horizontal dash in blocks
Role:
user
Media:
screen
Condition:
Normal

CSS

#outer #dashboard,
#main.dashboard {
  float: none;
  width: auto;
  max-width: 100%;
  margin: 1%;
  padding: 0;
  clear: both;
}

#dashboard ul.navigation {
  float: left;
  margin: 3.5%;
}

#dashboard .landmark {
  clear: none;
  float: left;
}