You could fake it, although you'll need a bit more markup. Using this HTML:
<div id="container">
<div class="imageWrapper">
<span class="fakeRowBorder">clever, huh? ;-)</span>
<img src="somesrc" />
</div>
<div class="imageWrapper">
<span class="fakeRowBorder">clever, huh? ;-)</span>
<img src="somesrc" />
</div>
... [etc.]
</div>
And this CSS:
#container{position:relative;width:400px;}
img{width:50px;height:50px;outline:1px dotted green}
.imageWrapper{float:left;position:static;margin-bottom:30px;}
.fakeRowBorder{position:absolute;left:40px;right:40px;margin-top:55px;border-bottom:1px solid blue;text-align:center;font-size:9px}
As long as .imageWrappers are static (by default), absolutely positioned .fakeRowBorders will use #container as a reference grid for any positioning properties (top, right, bottom, or left). If you don’t point above or below on these fake borders, then they will be calculated on how they would be if they were located normally (instead of accepting 0 by default, as one might think), and that trick : Specify "left" and "right" for each of them, but leave the "upper" and "lower" undefined.
.
, :
http://jsfiddle.net/5S6j9/3/
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