Edit line thickness of CSS 'underline' attribute

Question

Since you can underline any text in CSS like so:

h4 {
    text-decoration: underline;
}

How can you also then edit the \'line\' that is drawn

Answer 1

Very easy ... outside "span" element with small font and underline, and inside "font" element with bigger font size.

 
   Text with big font size and thin underline