<p dir="auto">You can reproduce it with in <a href="http://getbootstrap.com/javascript/#modals" rel="nofollow">http://getbootstrap.com/javascript/#modals</a> "Launch Demo Modal".</p>
<p dir="auto">The body displaces 15px when the modal is open.</p>
<p dir="auto">This happens only in Safari ( tested in 6.0.5 )</p>
<p dir="auto"><a target="_blank" rel="noopener noreferrer nofollow" href="https://camo.githubusercontent.com/56c298e361685ece65b67b3c92795d09c878cd8a534f1e08b7ca15f0c21b19d6/68747470733a2f2f662e636c6f75642e6769746875622e636f6d2f6173736574732f33383334372f313035313535302f66616232393262632d313063632d313165332d383436632d3461613535666532383563372e706e67"><img src="https://camo.githubusercontent.com/56c298e361685ece65b67b3c92795d09c878cd8a534f1e08b7ca15f0c21b19d6/68747470733a2f2f662e636c6f75642e6769746875622e636f6d2f6173736574732f33383334372f313035313535302f66616232393262632d313063632d313165332d383436632d3461613535666532383563372e706e67" alt="safari-issue" data-canonical-src="https://f.cloud.github.com/assets/38347/1051550/fab292bc-10cc-11e3-846c-4aa55fe285c7.png" style="max-width: 100%;"></a></p>
<p dir="auto">When launching the modal component (<a href="http://getbootstrap.com/javascript/#modals" rel="nofollow">http://getbootstrap.com/javascript/#modals</a>) the entire content will slightly move to the left on mac OS (haven't tried it on windows yet). With the active modal the scrollbar seem to disappear, while the content width still changes.</p>
<p dir="auto">You can observer the problem on the bootstrap page</p>