Developer's manual

Potential HTML conflicts

The most significant potential conflict is with malformed HTML - the navigation structure is vulnerable to coding errors earlier on the page. If you have any layout or configuration problems, the first thing to do is validate the page it's on. Opera has a useful feature for this - you can validate local pages from the document context menu.

Other than that, the only HTML conflicts you're likely to encounter are with windowed controls, iframes or Flash movies.

Windowed controls

Windowed controls are objects which are rendered by the OS, rather than by the browser; some have a z-order of infinity, so if another element is positioned above it, the object will show through. The most common example of this is the <select> element in Windows Internet Explorer 5 and 6.

Thankfully, for Win/IE5.5-6 this problem is a thing of the past. Using a trick known as the Iframe shim it's possible to have DHTML layers above <select> elements, without them showing through. This technique is so robust that the menus can go above any embedded content, even Java applets or media players!

(The <iframe> is hidden with opacity so that you can still have transparent content in the menus. Opacity is rendered using Direct X, which in Internet Explorer is an ActiveX control (at the same security level as plugins like Flash), so for anyone who has Active-X disabled completely the <iframe> will have a white background).

This trick doesn't work for Win/IE 5.0, so the script also includes a conventional hiding routine that makes <select> elements invisible when the menus are open. This routine, and the iframe shim, are controllable with the manage windowed controls for win/ie variable.

No other supported browsers have a problem with <select> elements, but some may have problems with iframes or Flash movies:


Opera 7 and 8, Konqueror 3, Mac/IE5 and Win/IE5.0 cannot place menus above an <iframe>. There is no workaround, and auto-hiding iframes would look disturbing; so I suggest you try to design around the co-incidence of menus and iframes, as far as possible.

Flash movies

In Win/IE5.5-6, Flash movies are not an issue because of the trick used to keep menus above windowed controls. But for other browsers there's a couple of extra steps you can take, which should allow the menus to go above Flash:

  1. The Flash object must be positioned so that it can have a z-index; the z-index should be lower than the navbar's base z order.
  2. Enable wmode transparency using either: <param name="wmode" value="transparent" /> within an <object>, or the wmode attribute of <embed> - wmode="transparent".

Some users have reported that this only works in Firefox if the wmode parameter has the value "opaque". There's a test page for these parameters at

For further documentation please visit the Macromedia Flash Support Center.


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