Please look at the code:

<div class="square" style="height:1in;width:1in;">width 1in</div><br /> <div class="square" style="width:2.54cm;">width 2.54cm</div><br /> <div class="square" style="width:72pt;">width 72pt</div><br /> <div class="square" style="width:96px;">width 96px</div><br />

All bars should have the same width but the 96px bar is smaller… a 97px matches so i think the internal factor is wrong or rounded to much or something like that.
A global scale should not do something on the relative size of the elements to each other 1inch = 2.54 cm; 1inch = 72 pt; 1inch = 96px <- and it looks like this is actually 1inch = 97px The match of real paper inch don't matter here.