Simple WordPress Loop - Smartupworld

The Loop

<?php
if ( have_posts() ) {
    while ( have_posts() ) {
        the_post();

<!-- Test if the current post is in category 3. -->
    <!-- If it is, the div box is given the CSS class "post-cat-three". -->
    <!-- Otherwise, the div box is given the CSS class "post". -->

    <?php if ( in_category( '3' ) ) : ?>
        <div class="post-cat-three">
    <?php else : ?>
        <div class="post">
    <?php endif; ?>

<!-- Display the Title as a link to the Post's permalink. -->

<h2><a href="<?php the_permalink(); ?>" rel="bookmark" title="Permanent Link to <?php the_title_attribute(); ?>"><?php the_title(); ?></a></h2>

<small><?php the_time('F jS, Y'); ?> by <?php the_author_posts_link(); ?></small>

<div class="entry">
        <?php the_content(); ?>
    </div>

<p class="postmetadata"><?php _e( 'Posted in' ); ?> <?php the_category( ', ' ); ?></p>
    </div> <!-- closes the first div box -->

} // end while 
} // end if 

?>

See More at - 
Codex: The Loop