This is because label
is an inline element, and is therefore only as big as the text it contains.
The possible is to display your label
as a block element like this:
#formItem label {
display: block;
text-align: center;
line-height: 150%;
font-size: .85em;
}
However, if you want to use the label on the same line with other elements, you either need to set display: inline-block;
and give it an explicit width (which doesn't work on most browsers), or you need to wrap it inside a div
and do the alignment in the div
.