text-align: center;
A block of text is a stack of
line boxes.
In the case of 'start', 'end', 'left', 'right' and 'center', this
property specifies how the inline boxes within each line box align
within the line box: alignment is not with respect to the
viewport
or containing block. In the case of 'justify', the UA may stretch
the inline boxes in addition to adjusting their positions. (See also
the 'text-justify',
'text-justify-trim',
'text-kashida-space',
'letter-spacing'
and 'word-spacing')
W3C Working Draft 6 March 2007.