White bars left of <a>-tags on colored background in Firefox

[Manfred Kooistra]

I have positioned a text link over an image, and when I hover over the
link, in Firefox a 1px-wide text-high white bar appears immediately to
the left of the first letter of this link. CSS for the <a>-tag is:

A:link { text-decoration: none; color: #660000; }
A:visited { text-decoration: none; color: #660000; }
A:hover { text-decoration: none; color: #CC0000; }
A:active { text-decoration: none; color: #CC0000; }

I had the same problem with image-links, and here the following
suppressed the white line:

A.imagelink:hover { text-decoration: none; color: #660000; }
<a href="..." class="imagelink">

But I cannot do this to a text link, as I want the color to change on
hover.

Am I stupid, or what can I do?

The relevant page is located at
www.manfredkooistra.de/24021967/fotografien.html. (Attention! One link
leads to adult content. Do not follow, if offended.)