priyankabhar on "how to reduce the width of footer in twenty eleven"

Thank you for replying. I used

#colophon {
	margin:auto;
	width: 900px;
}
#site-generator {display:none; }

to center my footer which I included as under:

<?php include(ABSPATH . "../footer.php"); ?>
			<div id="site-generator">
				<?php do_action( 'twentyeleven_credits' ); ?>
				<a href="<?php echo esc_url( __( 'http://wordpress.org/', 'twentyeleven' ) ); ?>" title="<?php esc_attr_e( 'Semantic Personal Publishing Platform', 'twentyeleven' ); ?>" rel="generator"><?php printf( __( 'Proudly powered by %s', 'twentyeleven' ), 'WordPress' ); ?></a>

Is this the right way?

Also I get many errors while validating, and most of them are from wordpress like

Line 238, Column 189: Attribute pubdate not allowed on element time at this point.
…me="2012-12-22T03:46:55+00:00" pubdate>December 22, 2012</time><span class…
Attributes for element time:

How can I remove such errors or can I just leave them as they are? I validated for HTML5.

Thanks,
Priya