How to select first and last TD in a row?

You can use the following snippet:

  tr td:first-child {text-decoration: underline;}
  tr td:last-child {color: red;}

Using the following pseudo classes:

:first-child means "select this element if it is the first child of its parent".

:last-child means "select this element if it is the last child of its parent".

Only element nodes (HTML tags) are affected, these pseudo-classes ignore text nodes.