There's no visual clue what form element is currently selected which may impact accessibility (https://github.com/piwik/piwik/issues/4167).
As mentioned on Piwik forum: http://forum.piwik.org/read.php?3,118149
"I noticed on the Login-form, that when moving from field to field with the tab key,
there's no visual indicator when the focus is on the checkbox or the submit button.
On textfields the blinking cursor is the only indicator."
The default light-blue border over input is usually sufficient clue that input is selected.
Thanks for the nice suggestion! +1 for the light blue border (or maybe we can reuse an existing Themed color)
This was recently fixed during the Catalyst Academy. A dark / grayish color was used. I think the related PR is #7035