make a backup copy of your theme files before editing
if you insert these styles at the end of style.css, there should be no side effect on any header or menu tabs:
.entry-utility {display:none; }
.entry-meta {display:none; }
you can do it the hard way and edit loop.php and locate and remove the code there:
around line 135:
<div class="entry-meta">
<?php twentyten_posted_on(); ?>
</div><!-- .entry-meta -->
and from line 148:
<div class="entry-utility">
<?php if ( count( get_the_category() ) ) : ?>
all the way down to (inclusive):
<?php edit_post_link( __( 'Edit', 'twentyten' ), '<span class="meta-sep">|</span> <span class="edit-link">', '</span>' ); ?>
</div><!-- .entry-utility -->
2.
either:
#site-info { display: none; }
or edit footer.php and delete:
<div id="site-info">
<a href="<?php echo home_url( '/' ); ?>" title="<?php echo esc_attr( get_bloginfo( 'name', 'display' ) ); ?>" rel="home">
<?php bloginfo( 'name' ); ?>
</a>
</div><!-- #site-info -->
--------
the black line:
in style.css;
replace the border-top: 4px solid #000; with border-top: none; in the following style:
#colophon {
border-top: 4px solid #000;
margin-top: -4px;
overflow: hidden;
padding: 18px 0;
}