title: scrollTop inconsistencies when (zoom < 1)
body: <p><em>This is my first SO question, so please forgive any question faux-pas!</em></p>
  
  <p>I have two containers on my HTML DOM that float:left. Each has content that must be perfectly aligned with the other. The left container (A) has overflow-y:hidden while the right container (B) has overflow-y:scroll. I use an onscroll callback to set the scroll position of container A like such:</p>
  
  <pre><code>    A.scrollTop = B.scrollTop;
  </code></pre>
  
  <p>This works great in 99% of use-cases... until a client zooms below 100%. When zoom is below this level, rows in one container are sometimes 1 pixel off from those in the other. My first guess is that this is a rounding issue, but I can't figure out where I can find values that I could use to build an algorithm to predict when &amp; how the error will occur. In addition, both containers have exactly the same height, and their content is of identical height as well, so I'd expect any rounding errors to be the same for each of them!</p>
  
  <p><a href="http://jsfiddle.net/mattebel/57rw3/" rel="nofollow noreferrer"><strong>I've created a jsFiddle demonstrating the behavior here</strong></a>. (I've used divs in this example, but other elements exhibit the same behavior) (I'm testing in chrome)</p>
  
  <p><strong>Can anyone explain why these two containers exhibit different behaviors when setting scrollTop to the same value?</strong> Also, given that browser-zoom detection is difficult at best 
  <a href="https://stackoverflow.com/questions/1713771/how-to-detect-page-zoom-level-in-all-modern-browsers">(discussion here)</a> <strong>does anyone know an efficient way to identify and correct for this issue?</strong> </p>