Cant Preview my webpage

hello to all Dreamweaver users.

im making our own personal homepage.

ive set up manage the site in Dreamweaver CS4.
the problem is when i preview (F12) i got this error from my web browsers (Firefox and IE):
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http://localhost/index.html
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You are not authorized to view this page
You do not have permission to view this directory or page using the credentials you supplied.
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Please try the following:

* Click the Refresh button to try again with different credentials.
* If you believe you should be able to view this directory or
page, please contact the Web site administrator by using the
e-mail address or phone number listed on the localhost home
page.

HTTP 401.1 - Unauthorized: Logon Failed
Internet Information Services
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Technical Information (for support personnel)

* More information:
Microsoft Support
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i transfer my sites to my laptop and it works.

what seems to bet he problem?
can you help me please.