problem with html tag properties

with this code
<div style="width: 47px; float: left;">
some of onscreen items couldn't display

when i change to
<div style="width: 47%; float: left;">

things looking fine.
let me a msg if u know what's wrong with this.
thank you.

used codes reference: http://www.htmlcodetutorial.com/characterentities_famsupp_69.html