function select_platform(obj){
    platformdata=obj.value;
    document.feedback.product.options.length=0;
    document.feedback.product.options[0]=new Option('--choose product--','---');
    //s='';
    //s='<select name="product">';
    for(i=0;i<a.length;i++){
        if(platformdata.indexOf(a[i][0])!=-1){//got needed platform
            for(j=1;j<a[i].length;j++){
                document.feedback.product.options[j]=new Option(a[i][j],a[i][j]);
                //s+='<option>'+a[i][j];
                }
            }//if
        }//for i
    //s+='</select>';
    //producttd.innerHTML=s;
    return true;
    }