how to make comment, date, postedby, taxonomyterm in one line

The positioning of post info and taxonomy terms is controlled by your theme. In this case we're talking about the theme for your node. So you will need to make adjustments to the node.tpl.php file for your active theme.

Somewhere in that file you will find something like:

<?php if ($taxonomy): ?>
      <div class="terms"><?php print $terms ?></div>
    <?php endif;?>

This code controls where your taxonomy terms get printed.

You will also find something like:

<?php if ($submitted): ?>
      <span class="submitted"><?php print t('Submitted by !username on !date', array('!username' => theme('username', $node), '!date' => format_date($node->created))); ?></span>

This code controls the display of your node submission info.

You will need to cut the first bit of code and paste it directly after the second bit of code, but inside the span tags I believe.

Rob Safuto
Learn By The Drop is a place to learn Drupal. If you're new to Drupal I recommend having a look at my Beginner's Guide To Drupal.