The Flash Player has supported the wmode parameter since version 3. The default value for wmode is “window”, which causes the SWF movie to run in its own invisible window above all content in the browser window.
<param value="window">

This causes problems when using DHTML menus and the like. The solution for this is to set the wmode parameter to “opague” which makes the Flash Player render its content directly onto the browser’s window.

Setting the wmode to anything other than “window” (opague or transparent) solves the DHTML menu issue and other issues, but at the same time it creates a bunch of other problems to be aware of!

First of all it makes the Flash totally invisible for any screen readers, making the Flash pretty inaccessible.

Another issue is that it makes a mess concerning textfields and keyboard mappings in different browser like Firefox. For example I experienced that a small form I had created in a Flash banner was suddenly not able to create the ‘@’ character. Using AltGr+2 did not produce anything other than a ‘2’. Shift+2 on the other hand created the ‘@’ but I guess we can’t expect the users to figure that out. Luckily I got in contact with someone who had experienced this before and guided me to the right path of making sure that wmode should be set to “window”. After informing the responsible host for the Flashfile about the issue everything worked out fine and the users where again able to use the keyboard mappings as they were used to.

I’m sure there is more people out there than me that have experienced trouble when changing the wmode parameter. Would be good to have all the issues gathered together on one location to avoid going into another wmode trap in the future!