css растягивание блоков

.but_menu {
    text-align:center;

}
a.button_menu {
float: left;
    outline: none;
letter-spacing: 0.1em;
    font: normal 100% 'lucida sans unicode', arial, sans-serif;
    display: block;
    height: 37px;
    padding: 29px 26px 6px 26px;
    text-align: center;
    color: #FFF;
    text-transform: uppercase;
    text-decoration: none;
    background: transparent;

}
 a.button_menu:hover {
    outline: none;
    text-decoration: underline;
color: #FFF;
  background: #1C2C3E url(style/menu_select.png) repeat-x;
}
#main, #logo, #menubar, #site_content, #footer, .but_menu
{ margin-left: auto; 
  margin-right: auto;
  }
#menubar, .but_menu
{ 
  height: 72px;
  vertical-align: middle;
  padding: 0;
  background: #29415D url(style/menu.png) repeat-x;
  
  } 
 сам код пхп
////////////////////////
echo'<div class="but_menu"><a class="button_menu" href="/id'.$user['id'].'"><center>'.$lang['my_page'].'</center></a>';
if($user['level']>1)echo'<a class="button_menu" href="/adm">'.$lang['adminka'].'</a>';
echo'<a class="button_menu" href="'.($new_mail>0?'/new_mess?':'/mail?').'">'.$lang['mail'].' '.$list.'</a>';
echo'<a class="button_menu" href="/kabinet">'.$lang['kabinet'].'</a>';
echo'<a class="button_menu" href="/exit">'.$lang['exit'].'</a></div>';