var box=new class_box();

function class_box(){

    this.init=function(){

        var my_div1=document.createElement('div');
        var my_div2=document.createElement('div');

        my_div1.id="box1";
        my_div1.style.width="100px";
        my_div1.style.height="100px";
        my_div1.style.backgroundColor="red";
        my_div1.style.display="block";

        my_div2.id="box2";
        my_div2.style.width="100px";
        my_div2.style.height="100px";
        my_div2.style.backgroundColor="green";
        my_div2.style.display="block";

        window.weiche(my_div1,"obj.style.styleFloat='left'","obj.style.cssFloat='left'");
        window.weiche(my_div2,"obj.style.styleFloat='left'","obj.style.cssFloat='left'");

        document.body.appendChild(my_div1);
        document.body.appendChild(my_div2);
    }


}

function weiche(my_obj,ie,moz,opera,other){

        obj=my_obj;

        if (navigator.appName.indexOf("Opera") != -1)
        {
            //opera
            eval(opera);
        }
        else if (navigator.appName.indexOf("Explorer") != -1)
        {
            //ie

            eval(ie);

        }
        else if (navigator.appName.indexOf("Netscape") != -1)
        {
            //netscape
            eval(moz);

        }
        else
        {
            //other
            eval(other);
        }
}