elInput = document.createElement("input");
elInput.name="IEtestFoo";
document.body.appendChild(elInput);
try{
    document.getElementsByName("IEtestFoo")[0].value="foobared";
    var isCrappyIE = false;
}catch(e){
    var isCrappyIE = true;
}

[...]
input		= isCrappyIE ? '<input name="x_'+booths[i].id+'">' : 'input';
var hiddenX	= document.createElement(input);