Menú con Dreamweaver (spyassets)

Hola ,
tengo un problema con la anchura del menú creado con Dreamweaver. En monitores cuadrados y móviles, el munú ocupa 2 líneas en lugar de una.
Quisiera dejar una anchura al 80%. Imagino que habrá que tocar alguna condición de la hoja de estilos que me creó el dreamweaver y que se llama sprymenubarhorizontal.css
Os paso el código a ver si alguien me puede decir qué tengo que modificar para que la anchura sea siempre del 80% independientemente del dispositivo o monitor donde se vea. Yo he intentado modificar varias cosas, sin resultado.
Muchas gracias de antemano.

@charset "UTF-8";

/* SpryMenuBarHorizontal.css - version 0.6 - Spry Pre-Release 1.6.1 */

/* Copyright (c) 2006. Adobe Systems Incorporated. All rights reserved. */

/*******************************************************************************

LAYOUT INFORMATION: describes box model, positioning, z-order

*******************************************************************************/

/* The outermost container of the Menu Bar, an auto width box with no margin or padding */
ul.MenuBarHorizontal
{
margin: 0;
padding: 0;
list-style-type: none;
font-size: 100%;
cursor: default;
width: inherit;

}
/* Set the active Menu Bar with this class, currently setting z-index to accomodate IE rendering bug: http://therealcrisp.xs4all.nl/meuk/IE-zindexbug.html */
ul.MenuBarActive
{
z-index: 1000;
}
/* Menu item containers, position children relative to this container and are a fixed width */
ul.MenuBarHorizontal li
{
margin: 0;
padding: 0;
list-style-type: none;
font-size: 100%;
position: relative;
text-align: center;
cursor: pointer;
width: inherit;
float: left;
}
/* Submenus should appear below their parent (top: 0) with a higher z-index, but they are initially off the left side of the screen (-1000em) */
ul.MenuBarHorizontal ul
{
margin: 0;
padding: 0;
list-style-type: none;
font-size: 100%;
z-index: 1020;
cursor: default;
width: 8.2em;
position: absolute;
left: -1000em;
}
/* Submenu that is showing with class designation MenuBarSubmenuVisible, we set left to auto so it comes onto the screen below its parent menu item */
ul.MenuBarHorizontal ul.MenuBarSubmenuVisible
{
left: auto;
}
/* Menu item containers are same fixed width as parent */
ul.MenuBarHorizontal ul li
{
width: 8.2em;
text-align: left;
border-bottom-width: thin;
border-bottom-color: #6A0000;
border-bottom-style: inset;
}
/* Submenus should appear slightly overlapping to the right (95%) and up (-5%) */
ul.MenuBarHorizontal ul ul
{
position: absolute;
margin: -5% 0 0 95%;
}
/* Submenu that is showing with class designation MenuBarSubmenuVisible, we set left to 0 so it comes onto the screen */
ul.MenuBarHorizontal ul.MenuBarSubmenuVisible ul.MenuBarSubmenuVisible
{
left: auto;
top: 0;
}

/*******************************************************************************

DESIGN INFORMATION: describes color scheme, borders, fonts

*******************************************************************************/

/* Submenu containers have borders on all sides */
ul.MenuBarHorizontal ul
{
border: 1px solid #CCC;
}
/* Menu items are a light gray block with padding and no text decoration */
ul.MenuBarHorizontal a
{
display: block;
cursor: pointer;
padding: 0.5em 0.75em;
color: #A40000;
text-decoration: none;
background-color: #CCCCCC;
font-family: Arial, Helvetica, sans-serif;
font-style: normal;
font-weight: normal;
}
/* Menu items that have mouse over or focus have a blue background and white text */
ul.MenuBarHorizontal a:hover, ul.MenuBarHorizontal a:focus
{
background-color: #33C;
color: #FFF;
text-align: left;
}
/* Menu items that are open with submenus are set to MenuBarItemHover with a blue background and white text */
ul.MenuBarHorizontal a.MenuBarItemHover, ul.MenuBarHorizontal a.MenuBarItemSubmenuHover, ul.MenuBarHorizontal a.MenuBarSubmenuVisible
{
background-color: #33C;
color: #FFF;
}

/*******************************************************************************

SUBMENU INDICATION: styles if there is a submenu under a given menu item

*******************************************************************************/

/* Menu items that have a submenu have the class designation MenuBarItemSubmenu and are set to use a background image positioned on the far left (95%) and centered vertically (50%) */
ul.MenuBarHorizontal a.MenuBarItemSubmenu
{
background-image: url(SpryMenuBarDown.gif);
background-repeat: no-repeat;
background-position: 95% 50%;
}
/* Menu items that have a submenu have the class designation MenuBarItemSubmenu and are set to use a background image positioned on the far left (95%) and centered vertically (50%) */
ul.MenuBarHorizontal ul a.MenuBarItemSubmenu
{
background-image: url(SpryMenuBarRight.gif);
background-repeat: no-repeat;
background-position: 95% 50%;
}
/* Menu items that are open with submenus have the class designation MenuBarItemSubmenuHover and are set to use a "hover" background image positioned on the far left (95%) and centered vertically (50%) */
ul.MenuBarHorizontal a.MenuBarItemSubmenuHover
{
background-image: url(SpryMenuBarDownHover.gif);
background-repeat: no-repeat;
background-position: 95% 50%;
}
/* Menu items that are open with submenus have the class designation MenuBarItemSubmenuHover and are set to use a "hover" background image positioned on the far left (95%) and centered vertically (50%) */
ul.MenuBarHorizontal ul a.MenuBarItemSubmenuHover
{
background-image: url(SpryMenuBarRightHover.gif);
background-repeat: no-repeat;
background-position: 95% 50%;
}

/*******************************************************************************

BROWSER HACKS: the hacks below should not be changed unless you are an expert

*******************************************************************************/

/* HACK FOR IE: to make sure the sub menus show above form controls, we underlay each submenu with an iframe */
ul.MenuBarHorizontal iframe
{
position: absolute;
z-index: 1010;
filter:alpha(opacity:0.1);
}
/* HACK FOR IE: to stabilize appearance of menu items; the slash in float is to keep IE 5.0 from parsing */
@media screen, projection
{
ul.MenuBarHorizontal li.MenuBarItemIE
{
display: inline;
f\loat: left;
background: #FFF;
}
}

Tengo dudas, pero creo que en esa hoja de estilo no puedes cambiar el tamaño del menú, ya que en ella sólo se hace referencia a los elementos ul, y la propiedad "width: inherit;" indica que la anchura del elemento se hereda del elemento padre.
Imagino que donde se debería cambiar el tamaño es en el elemento "MenuBarHorizontal".
De todas maneras lo mejor sería que realizaras tú,a mano la maquetación, así sabrías que valor corresponde cada elemento.
Suerte y un saludo!