Flash has these bright yellow borders around buttons and other MovieClips, when the user uses his tab keys. I haven’t found a way to change the look of these borders yet, so in the meantime, to have them disabled, I use following short code snippet:

Button.prototype.tabEnabled=false;
for(var obj in _root){
   _root[obj].tabEnabled = false;
   _root[obj]._focusrect=false;
}