function offSet(){
var message = confirm('是否确定取消设置?');
var txt1 = docement.getElementById('txt')
if(massage == true){
txt1.removeAttribute('style');
}
document写错了
var txt1=document..getElementById('txt')
这行代码要放到if判断语句里面去
txt1.style="";
替换成空字符串就行了