Spry Menu Bar jumps off screen-right in CS6

Question

Frustrating little glitch I'm experiencing.  When in a NON-LIVE mode in CS6, I have a Spry Menu Bar that I've placed, customized and is functioning properly.  It is precisely in the right location in BOTH live mode and in a browser preview, however, when I am editing the site the menu bar jumps off screen right to where I have to scroll right to locate it.  The only thing that pops it back in to place is by tweaking a setting like "Float" from right to left then back to right.  But once I begin to edit the site again it will jump off the screen.  This isn't a massive deal since it remains in place in live and preview modes, it's just annoying for layout purposes while I'm editing.  It sort of screws up the aesthetic of the layout.  Has anyone found the same problem?  Below is my layout.css and my Spry Menu css.
@charset "utf-8";
/* Simple fluid media
   Note: Fluid media requires that you remove the media's height and width attributes from the HTML
   http://www.alistapart.com/articles/fluid-images/
img, object, embed, video {
    max-width: 100%;
/* IE 6 does not support max-width so default to width 100% */
.ie6 img {
    width:100%;
    Dreamweaver Fluid Grid Properties
    dw-num-cols-mobile:        6;
    dw-num-cols-tablet:        8;
    dw-num-cols-desktop:    12;
    dw-gutter-percentage:    15;
    Inspiration from "Responsive Web Design" by Ethan Marcotte
    http://www.alistapart.com/articles/responsive-web-design
    and Golden Grid System by Joni Korpi
    http://goldengridsystem.com/
/* Mobile Layout: 480px and below. */
.gridContainer {
    margin-left: auto;
    margin-right: auto;
    width: 95.8695%;
    padding-left: 1.0652%;
    padding-right: 1.0652%;
#LayoutDiv1 {
    clear: both;
    float: left;
    margin-left: 0;
    width: 100%;
    display: block;
#header {
    clear: both;
    float: left;
    margin-left: 0;
    width: 100%;
    display: block;
#maincontent {
    clear: none;
    float: left;
    margin-left: 2.6785%;
    width: 100%;
    display: block;
#navigation {
    clear: none;
    float: left;
    margin-left: auto;
    width: 100%;
    display: block;
    margin-top: 20px;
    margin-bottom: 20px;
    background-color: #300;
    height: 16px;
    top: 5px;
#footer {
    clear: both;
    float: left;
    margin-left: 0;
    width: 100%;
    display: block;
    color: #FFF;
    background-attachment: fixed;
    background-image: url(../bkgdContent.png);
    background-repeat: repeat;
    margin-top: 20px;
/* Tablet Layout: 481px to 768px. Inherits styles from: Mobile Layout. */
@media only screen and (min-width: 481px) {
.gridContainer {
    width: 91.4836%;
    padding-left: 0.7581%;
    padding-right: 0.7581%;
#LayoutDiv1 {
    clear: both;
    float: left;
    margin-left: 0;
    width: 100%;
    display: block;
#header {
    clear: both;
    float: left;
    margin-left: 0;
    width: 100%;
    display: block;
    text-align: center;
#maincontent {
    clear: none;
    float: left;
    margin-left: 1.6574%;
    width: 100%;
    display: block;
#navigation {
    clear: both;
    float: left;
    margin-left: 0;
    width: 100%;
    display: block;
    height: 16px;
#whf-content {
    clear: both;
    float: left;
    margin-left: 0;
    width: 100%;
    display: block;
#donatecontent {
    clear: none;
    float: left;
    margin-left: 1.6574%;
    width: 100%;
    display: block;
#theride-content {
    clear: both;
    float: left;
    margin-left: 0;
    width: 49.1712%;
    display: block;
#donate-content {
    clear: none;
    float: left;
    margin-left: 1.6574%;
    width: 49.1712%;
    display: block;
#footer {
    clear: both;
    float: left;
    margin-left: 0;
    width: 100%;
    display: block;
/* Desktop Layout: 769px to a max of 1232px.  Inherits styles from: Mobile Layout and Tablet Layout. */
@media only screen and (min-width: 769px) {
.gridContainer {
    width: 89.0217%;
    max-width: 1232px;
    padding-left: 0.4891%;
    padding-right: 0.4891%;
    margin: auto;
#LayoutDiv1 {
    clear: both;
    float: left;
    margin-left: 0;
    width: 100%;
    display: block;
#header {
    clear: both;
    float: left;
    margin-left: 0;
    width: 100%;
    display: block;
    color: #FFF;
#maincontent {
    clear: both;
    float: left;
    margin-left: 0;
    width: 32.6007%;
    display: block;
#navigation {
    clear: both;
    float: left;
    margin-left: 0;
    width: 100%;
    display: block;
#whf-content {
    clear: both;
    float: left;
    margin-left: 0;
    width: 32.6007%;
    display: block;
#donatecontent {
    clear: none;
    float: left;
    margin-left: 1.0989%;
    width: 100%;
    display: block;
#donate-content {
    clear: none;
    float: left;
    margin-left: 1.0989%;
    width: 32.6007%;
    display: block;
#footer {
    clear: both;
    float: left;
    margin-left: 0;
    width: 100%;
    display: block;
#theride-content {
    clear: none;
    float: left;
    margin-left: 1.0989%;
    width: 32.6007%;
    display: block;
#whf-content {
    font-family: Georgia, "Times New Roman", Times, serif;
SPRY CSS
@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: auto;
    float: right;
/* 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: left;
    cursor: pointer;
    width: 4.3em;
    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: 4.3em;
    position: relative;
    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
/* Submenus should appear slightly overlapping to the right (95%) and up (-5%) */
ul.MenuBarHorizontal ul ul
    position: relative;
    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
/* Menu items are a light gray block with padding and no text decoration */
ul.MenuBarHorizontal a
    display: block;
    cursor: pointer;
    background-color: #300;
    color: #FFF;
    text-decoration: none;
    font-size: 12px;
    font-family: Georgia, "Times New Roman", Times, serif;
    text-align: center;
    height: 16px;
    padding: 0px;
/* 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: #003;
    color: #FFF;
/* 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: #003;
    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;

Answer 1

Design view is not reliable.  Learn to work in Code View or Split View with Live View to check your layout.
Spry menus are not responsive so they will not work well in a Fluid Grid Layout.  Find a better menu system.
Project Seven Responsive Tabs
http://www.projectseven.com/products/tools/tpm2/tutorials/responsive/index.htm
10 Responsive Menus
http://speckyboy.com/2012/08/29/10-responsive-navigation-solutions-and-tutorials/
In the meantime,
It's often easier to work with an unstyled HTML page. 
To disable CSS, go to  View > Style Rendering > untick Display Styles. 
Or, use a Design-Time Style Sheet.
http://help.adobe.com/en_US/dreamweaver/cs/using/WScbb6b82af5544594822510a94ae8d65-7e17a.h tml
Nancy O.