Height bug on windows

[DNarra]

Hey i'm using the mapbox jquery plugin and i've found a strange bug that until now only affects windows pcs (on my mac and ipad works fine).
What is happening is that i want to use percentage to set an icon inside the map and if i set lets say, 50% for margin-top the icon is displayed like i have set it to margin-top=100%. Margin-left is displayed fine...
What can be happening here?

[DNarra]

Now i've tried top use just "top" instead of "margin-top" and it is displaying the icons on the right place...
Dunno why.