donde le estoy diciendo aqui que este centrado ???

[Durgeoble]

/* All the content boxes belong to the content class. */
.content {
position:relative; /* Position is declared "relative" to gain control of stacking order (z-index). */
width:auto;
min-width:120px;
margin:0px 210px 20px 170px;
border:1px solid black;
background-color:white;
padding:10px;
z-index:3; /* This allows the content to overlap the right menu in narrow windows in good browsers. */
}
#navAlpha {
position:absolute;
width:150px;
top:20px;
left:20px;
border:1px dashed black;
background-color:#eee;
padding:10px;
z-index:2;

/* Here is the ugly brilliant hack that protects IE5/Win from its own stupidity.
Thanks to Tantek Celik for the hack and to Eric Costello for publicizing it.
IE5/Win incorrectly parses the "\"}"" value, prematurely closing the style
declaration. The incorrect IE5/Win value is above, while the correct value is
below. See http://glish.com/css/hacks.asp for details. */
voice-family: "\"}\"";
voice-family:inherit;
width:128px;
}
/* I've heard this called the "be nice to Opera 5" rule. Basically, it feeds correct
length values to user agents that exhibit the parsing error exploited above yet get
the CSS box model right and understand the CSS2 parent-child selector. ALWAYS include
a "be nice to Opera 5" rule every time you use the Tantek Celik hack (above). */
body>#navAlpha {width:128px;}

#navBeta {
position:absolute;
width:190px;
top:20px;
right:20px;
border:1px groove black;
background-color:#eee;
padding:10px;
z-index:1;
/* Again, the ugly brilliant hack. */
voice-family: "\"}\"";
voice-family:inherit;
width:168px;
}
Te lo he dejado lo mas aseado posible, lo subrayado es lo que buscas