Bug 189382 [accessibility]Web Viewer content isn't accessible for some assistive tools.[0002]
Description: Web Viewer content isn't accessible for some assistive tools. At present, viewer use ajax structure, so view the html source can only see many reference to outer files. From accessibility point of view, some accessibility rules are based on html source code, so this rules cannot be satisfied. For example, table Header rule require using <th> tag, id and header attributes so that assistive reader tools can find out the link between header and detail data, but in BIRT, this can only be done through using "preview" servlet and will fail for "frameset" and "run".
viewer/org.eclipse.birt.report.viewer/src/org/eclipse/birt/report/viewer/utilities/WebViewer.java
*/
	final public static String DOC = "doc"; 
	/**
	 * Birt web viewer plugin id
	 */
	final public static String WebAppPlugin = ViewerPlugin.PLUGIN_ID;
	/**
	 * locale preference name
	 */
	final public static String USER_LOCALE = "user_locale"; 
	/**
	 * Preference key for SVG chart flag.
	 */
	final public static String SVG_FLAG = "svg_flag"; 
	/**
	 * Preference key for master page content flag.
	 */
	final public static String MASTER_PAGE_CONTENT = "master_page_content"; 
	
	final public static String PREVIEW_MAXROW = "preview_maxrow"; 
	
	/**
	 * Key to indicate the format of the preview.
	 */
	public final static String FORMAT_KEY = "FORMAT_KEY"; 
	/**
	 * Key to indicate the 'allowPage' control of the preview.
	 */
	public final static String ALLOW_PAGE_KEY = "ALLOW_PAGE_KEY"; 
	/**