I'm transforming an HTML site to WordPress, and it is done. Now it appears such as the total dimensions are reduced, however the models are correct (just like the initial HTML, i.e. 980px width etc.).

Help me with this.

<head>
<meta content="text/html; charset=utf-8" http-equiv="Content-Type">
<title><?php
    /*
     * Print the <title> tag based on what is being viewed.
     */
    global $page, $paged;

    wp_title( '|', true, 'right' );

    // Add the blog name.
    bloginfo( 'name' );

    // Add the blog description for the home/front page.
    $site_description = get_bloginfo( 'description', 'display' );
    if ( $site_description && ( is_home() || is_front_page() ) )
        echo " | $site_description";

    // Add a page number if necessary:
    if ( $paged >= 2 || $page >= 2 )
        echo ' | ' . sprintf( __( 'Page %s', 'twentyten' ), max( $paged, $page ) );

    ?></title>
<link rel="profile" href="http://gmpg.org/xfn/11" />
<link rel="stylesheet" type="text/css" media="all" href="<?php bloginfo( 'stylesheet_url' ); ?>" />
<link rel="pingback" href="<?php bloginfo( 'pingback_url' ); ?>" />
</head>

Look at your styles once more. Might be other kinds may contradict using the width. Would you please provide more details excatly?

Yes, more information could be useful. The odds are good Wordpress is connecting to a different stylsheet you do not know about. Are you currently utilizing a theme? It's most likely got it's own stylesheet, or any other wordpress plugin is adding it's own style.