I got a 403 page(not authorized) in the last step of the Installation

When i use the id(admin) that the wp gave me and the password to login at the first time, i got a 403page as follow:
You are not authorized to view this page
You might not have permission to view this directory or page using the credentials you supplied.

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If you believe you should be able to view this directory or page, please try to contact the Web site by using any e-mail address or phone number that may be listed on the XXXXXX.XXXX.com home page.

You can click Search to look for information on the Internet.

HTTP Error 403 – Forbidden
Internet Explorer

what shall i do?