Update: Fri, Jan 24 2014 9:30 PM UTC
The issue with accessing www.visualstudio.com is now mitigated. We had updated a DNS record that was pointing to an incorrect alias, which was causing the issue. At this point, customers should not experience any issues accessing the site. We apologize for the inconvenience and appreciate your patience as we worked to resolve this issue
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Initial Update: Fri, Jan 24 2014 at 20:40 UTC:
Some customers are experiencing issues with the www.visualstudio.com and tfs.visualstudio.com websites. This appears to be a DNS issue and is not impacting Visual Studio Online services when navigating to http://<accountname>.visualstudio.com/ directly.
Our DevOps are engaged and actively working to resolving the issue.