[austinlyons]

Wouldn't you just instead write the CSS as follows?

  .sidebar.title {
    text-decoration: underline;
  }

[talmand]

That likely wouldn't have the intended effect as I find it doubtful that the element with the sidebar class would also be the title.

[lstamour]

Well, you could also write .sidebar > .title to be more specific than simply all .title elements in .sidebar, but the point is to not tie your CSS quite so closely to the HTML hierarchy I suppose.