Space between two rows in a table?

Is this possible via CSS?

I’m trying

tr.classname {
  border-spacing: 5em;
}

to no avail. Maybe I’m doing something wrong?

In the parent table, try setting

border-collapse:separate; 
border-spacing:5em;

Plus a border declaration, and see if this achieves your desired effect.
Beware, though, that IE doesn’t support the “separated borders” model.