Comment 1 for bug 595907

Even better markup:

    <a target="help" href="/+help/driver.html"
      class="sprite maybe">&nbsp;<span class="invisible-link">Driver help</span></a>

This is the zero-width problem. My fix to the formatters was to ensure there is always a space in the link.

ObjectImageDisplayAPI.boolean
    <span class="sprite %(icon)s">&nbsp;<span class="invisible-link">%(icon)s</span></span>

Note that we always want to place an &nbsp; before the invisible-link element, or in the anchor if it is being left empty.