cesium funny behavior

I have this dynamically generated by a javascript :

var t = document.getElementById(\"outcell\");
// outcell is a <td>,
//it is correctl defined

var div = document.createElement('div');

div.style.border = '2px solid white';
div.width = '98%';
div.padding = '4px';
div.margin = '4px'; // viewer injected .....

Thus, I am dynamically generating a div ...

Now, a php script is writing this to after the javascript, before the loading of course :

$cn = 1;
echo "var map".$cn." = new Cesium.CesiumWidget('cesiumContainer".$cn."', {
        sceneMode : Cesium.SceneMode.SCENE3D
        });\n"; // container, and viewmode
echo "var scene".$cn." = map".$cn.".scene;\n"; // scene injected
echo "var terrainProvider".$cn." = // etc

Everything is fine, but the div size seems to be increasing as loading progresses.... That is, the widget is growing by itself

What am i doing wrong? could not get any error in firefox js console.