Nachtrag:
function dragstart(element,marginLeft,marginTop) {
if (busy == 0) {
busy = 1;
dragobjekt = element;
dragx = posX - dragobjekt.offsetLeft + marginLeft;
dragy = posY - dragobjekt.offsetTop + marginTop;
}
}
(...)
<someTag style="left:200px; top:0px; margin-left:100px; width:50px;"
onclick="if(busy==0){javascript:dragstart(this,100,0);}
else{javascript:dragstop();}" ></someTag>