Bug 173582 Run servlet should not be affected by values in document.[0000]
viewer/org.eclipse.birt.report.viewer/birt/WEB-INF/classes/org/eclipse/birt/report/taglib/AbstractViewerTag.java
}
	/**
	 * Validate the viewer id. Viewer id only can include number, letter and
	 * underline
	 * 
	 * @return
	 */
	protected boolean __validateViewerId( )
	{
		Pattern p = Pattern.compile( "^\\w+$" ); 
		Matcher m = p.matcher( viewer.getId( ) );
		return m.find( );
	}
	/**
	 * Handle event before doEndTag
	 */
	protected void __beforeEndTag( )
	{
		super.__beforeEndTag( );
		viewer.setParameters( parameters );
		
		pageContext.setAttribute( viewer.getId( ), viewer.getId( ) );
		
		if ( viewer.isHostPage( ) )
			pageContext.setAttribute( ATTR_HOSTPAGE, "true" ); 
	}
	/**
	 * Handle use IFrame to preview report. Each IFrame should have an unique
	 * id.
	 *