maintainace for a Site

How to put maintaince for a site. In IIS.
If I have Type as www.xxx.com... it need to go to maintainance page.
how to put maintainace?
if i have Typed as www.xxx/yy/zz.aspx
xxx is sitename
YY is folder name
ZZ is page name
if i have Typed as www.xxx/yy/zz.aspx
it need to go to maintainance page.
i need to do in IIs.For root it going    properly.But for sub folder it not going it showing as 
Server Error in '/maint' Application.
Can any Explain in detail about maintance for site and Subfolder in the Site

thanks,
Priyanka
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