1. Open SharePoint 2010 Central Administration, Go to Manage Web Applications
Select Your Site and click on Authentication Providers icon in the top ribbon bar
Click on Default Zone and Check the Enable Anonymous Access CheckBox and save it
2. Select your site and click on Anonymous Policy Icon In ribbon
Select Default Zone from dropdown and select the permissions option you want to grant to anonymous users Selecting None - No Policy is recommended )
3. Close Central Administration and open your site collection in browser with administrator account (Site for which you just had set anonymous access)
Click on Site Actions and select Site Permissions
Click on Anonymous Access Icon on the top ribbon
Select Entire Web Site Option and click on OK
Now you can browse your site Anonymously without login.
Hope this helps.