The normal generated code for the Flash Badge is not W3C valid, like most generatet code for Flash.

 I've followed the the Flash Satay method to get it W3C valid.

 Get W3C in the following steps and use the generated code from Twitter, where your already chose a colour.

Step 1: Copy generated code from Twitter

The code which is generated on Twitter is:

<div style="width:176px;text-align:center">

     <embed src="http://twitter.com/flash/twitter_badge.swf"  flashvars="color1=10658507&type=user&id=16628636"  quality="high" width="176" height="176" name="twitter_badge" align="middle" allowScriptAccess="always" wmode="transparent" type="application/x-shockwave-flash" pluginspage="http://www.macromedia.com/go/getflashplayer" />

     <br>

     <a style="font-size: 10px; color: #A2A2CB; text-decoration: none" href="http://twitter.com/Skaninchen">follow Skaninchen at http://twitter.com</a>

</div>

Step 2: Delete all dispensable code

You only need the following code and note that the color and userid should be different, because these is an example.

http://twitter.com/flash/twitter_badge.swf

color1=10658507&type=user&id=16628636

width="176" height="176"

<a style="font-size: 10px; color: #A2A2CB; text-decoration: none" href="http://twitter.com/Skaninchen">follow Skaninchen at http://twitter.com</a>

Step 3: Make an object

Put the url to the .swf in the data and write "?path=&" and then paste the colour and userid, followed by the indications.

At value of the param name the same long url like in data again.

 <object type="application/x-shockwave-flash" data="http://twitter.com/flash/twitter_badge.swf?path=&color1=10658507&type=user&id=16628636" width="176" height="176">

        <param name="movie" value="http://twitter.com/flash/twitter_badge.swf?path=&color1=10658507&type=user&id=16628636" />

  </object>

Step 4: Valid code

Example: http://ferdy.sohosted.com/maikel/mariposa/

<div style="width:176px;text-align:center">

    <object type="application/x-shockwave-flash" data="http://twitter.com/flash/twitter_badge.swf?path=&color1=10658507&type=user&id=16628636" width="176" height="176">

        <param name="movie" value="http://twitter.com/flash/twitter_badge.swf?path=&color1=10658507&type=user&id=16628636" />

    </object>

     <br />

    <a style="font-size: 10px; color: #A2A2CB; text-decoration: none" href="http://twitter.com/Skaninchen">follow Skaninchen at http://twitter.com</a>

</div>

Notice that <br> is not W3C valid and should be replaced by <br />