From Birnam Designs Wiki

Dotted borders around active links can detract from a design -- although their usability improvement should not be overlooked, sometimes a designer needs to take control over this. I have found this especially annoying around flash elements, where there is no usability advantage. Remove with this css:

object:active { outline: none; }
object:focus { -moz-outline-style: none; }
embed:active { outline: none; }
embed:focus { -moz-outline-style: none; }
a:active { outline: none; }
a:focus { -moz-outline-style: none; }