you cannot put a <hr/> inside a <p>... you shouldn't put anything that constitutes a block ( this includes hr, a div, or another p ) inside a p

For example:
It's usually quite easy to terminate <p>s correctly..

To horizontally center any block level element (like a table) you can use CSS like this:


With your textarea; in some browsers, they adjust their height to a multiple of the row height ( which is affected by the font-size/family ).
I would say, you might be better off using a different element to display content. If you don't want the textarea font to change but you're changing a page-wide (body) font; you might want to exclude the textarea, by means of giving it a certain font/size in CSS. Otherwise; you may have difficulty getting around this in a 'non-hacky' way. You can set the 'line-height' in CSS; but if it's small, it crops the top/bottom of big text..