tooltip bug

I just noticed some odd behaviour with

<img src=img title="img title" border=1 width=50 height=50><br>
<a href=link title="link title">text</a>

If I put the cursor over the link and then, when I expect the
tooltip to pop up, move quickly up into the image, first the link's
tooltip pops up for an instant -- but says "img title" -- and then the
image's tooltip pops up -- but says "link title".