How to check if css property is set?
<p>As per the title really.</p>

<p>If notice that if I check <code>$(elem).css('margin-top')</code> it returns <code>0px</code> even though I haven't explicitly set this style, either inline or in a stylesheet.</p>

<p>Basically I am setting the margin each time I hover over an element (to vertically align some content) so would rather just do this once.</p>

<p>I can't set the alignment on page load because the elements are hidden (display:none) so it needs to be done at the time they are displayed.</p>
