First of all, you should probably use <button>
instead of <a href="#">
. Empty links can be confusing for screen readers, but a button is a button. In short, links take you places, buttons perform actions. (http://www.karlgroves.com/2013/05/14/links-are-not-buttons-neither-are-divs-and-spans/; https://ux.stackexchange.com/questions/5493/what-are-the-differences-between-buttons-and-links).
I would go with a variation of your first code sample, and utilize Bootstraps .sr-only
class. If we update your code with button
and add in the class, we have:
<button type="button" class="btn btn-default"><span class="fa fa-pencil"></span> <span class="sr-only">Edit</span></button>
We now have a more semantically correct button element; sighted users see the edit pencil icon; and screen reader users will hear "Edit". Everyone wins.
(Note, the button
code is straight from Bootstraps CSS Buttons section.)