Ciao, premetto che hai sbagliato categoria... sarebbe più appropriata la categoria CSS...

dovresti portare fuori dal <div class="toptabs"> i <div class="tabbox"> così :

codice:
<div id="front">
    <div class="toptabs">
        <ul class="toptablist">[*]Video[*]Popular[*]Top Rated[*]Comments[/list]
        <div class="clear"></div>
    </div>
    <div class="clear"></div>
    <div class="clear"></div>
    <div id="video">	
        <div class="tabbox" style="display: block; ">
            <div class="videotab">
                <object width="560" height="315"><param name="movie" value="http://www.youtube.com/v/8idAQpUX3gM?fs=1&amp;hl=en_US"><param name="allowFullScreen" value="true"><param name="allowscriptaccess" value="always"><embed src="http://www.youtube.com/v/8idAQpUX3gM?fs=1&amp;hl=en_US" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="560" height="315"></object>
            </div>
            <p class="morevideo">View all</p>
        </div>
        <div class="tabbox" style="display: none; ">
            
  1. 
                    VINCI “A NIGHT LIKE THIS FESTIVAL”
                    <span class="commentcount" title="Comments">18</span>
  2. 
                    Vinci “Vinile Festival”
                    <span class="commentcount" title="Comments">14</span>
  3. 
                    Vinci “Anniversary Basstation”
                    <span class="commentcount" title="Comments">10</span>
  4. 
                    Vinci “THE DUB SYNC”
                    <span class="commentcount" title="Comments">9</span>
                
                <li style="border-bottom-width: 0px; ">
                    LiveMi??…no…Pisapia VS Red Ronnie!!
                    <span class="commentcount" title="Comments">1</span>
                

        </div>
        <div class="tabbox" style="display: none; ">
            
        </div>
        <div class="tabbox" style="display: none; ">
            
  1. <div class="author-img"></div>the dub sync Melissa Pizzuto<div class="clear"></div>
  2. <div class="author-img"></div>the dub sync Tommaso<div class="clear"></div>
  3. <div class="author-img"></div>the dub sync Felice Giovinazzo<div class="clear"></div>
  4. <div class="author-img"></div>S Maty<div class="clear"></div>
  5. <div class="author-img"></div>S Giovanni<div class="clear"></div><li style="border-bottom-width: 0px; "><div class="author-img"></div>:) "S" Mari<div class="clear"></div>

        </div>
    </div>
</div>
ed aggiungere al css la seguente regola:
codice:
#video{width:560px /*la larghezza del video */; margin-left:auto;margin-right:auto}
ed eliminarli dal attributo style.

Spero di esserti stato di aiuto...