There appears to be a bug in Safari that causes <code>z-index</code> to be ignored when setting CSS animation/filter effects on one of the overlapping elements. The result in this case is that any portion of a hyperlink on <code>index.html</code> that falls inside the bounding rectangle of the large logo mark are not clickable.

The only good solution for now is to comment out the the <code>filter</code> property on the image.