How to access frame that highlight in red of frameset in other frameset ? Like below,
document.write('<frameset rows="80,*" cols="*" frameborder="NO" border="0" framespacing="0">');
        document.write('<frame src="header.html" name="header" scrolling="NO" noresize >');
            document.write('<frameset rows="*,66" frameborder="NO" border="0" framespacing="0">');
            document.write('<frameset name = "mainContent" cols="240,*" framespacing="0" frameborder="no" noresize="">');
                document.write('<frame src="navigation.html" name="nav" id="nav" scrolling="Auto" noresize>');
                document.write('<frame src="'+subpage+'" name="content" id="content" scrolling="Auto" noresize style="border:1px solid #cccccc;">');
            document.write('<\/frameset>');
            document.write('<frame name="footer" src="footer.html" scrolling="NO" noresize>');
        document.write('<\/frameset>');
    document.write('<\/frameset>');