代码：
master_headertop =document.getElementById('master_headertop');
if (master_headertop)
master_headertop.style.display = 'none';
错误提示：
Object doesn't support this property or method.更正为：
var master_headertop =document.getElementById('master_headertop');
if (master_headertop)
master_headertop.style.display = 'none';
以下也是错误的：
getElementById('master_headertop').style.display = 'none';