How to add Flash SWF as background of a HTML page?

I have a site and need to put swf file background of it and put other thing on it开发者_运维问答.how can i do that?

I don't understand why you could want to do that. In any case, there's no proper way of doing it through HTML only. Still, you could use the z-index CSS property, this way:

MyCSS.css

* {
    z-index: 1;
}

.mySWFBackground {
    z-index: 0;
}

After this, your SWF element (in the HTML) should have

class="mySWFBackground"

I have never done it before, but I imagine that there will be some weird output (like unselectable content or as such).

There seems to be a few results on google for doing this. You can't actually set an SWF as a background proper, but this guy was able to do it with a div tag: http://www.kirupa.com/forum/showthread.php?277976-Using-swf-as-CSS-background, and with javascript: http://manos.malihu.gr/flash-background-with-html-content and also using the z-index as Julian suggested.