Hi thuongquoc,
After searching some aritcles from brinkster.com, I think by default you have only one web application.
Can I have a virtual directory created in my web?
http://kb.brinkster.com/Kb.asp?kb=80778
How do I set up application roots?
http://kb.brinkster.com/Kb.asp?kb=110268
Hence, the “backup” folder under the web application folder is a sub-directory. Some sections such as “authentication” are not allowed to be defined in the web.cofig, which placed in the sub-directory. Therefore, please move the web.config file to “idqu” folder, or delete the web.config file from the “backup” folder.
By the way, I have modified your post to replace the user name and password to ****. Please change your password as soon as possible.
---idqu
------backup
---------web.config
------db
------images
The following section in web.config in sub directory “backup” is not allowed.
<authentication mode="Windows" />