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I've been having issues accessing stackoverflow for the last couple of days.

Today, I've tracked it down to having issues getting content from the CDN. It takes an age to load the page and it is missing the CSS and js files that make it look presentable, ad aloow voting etc.

If I view source and try to download the linked css file directly I get the follwoing message:

"The proxy cannot establish a connection to the web server: /".

This is accessing from work in the UK. I've not tried from home, yet.

Is this issues affecting anyone else? Is it just my office proxy and I need to catch our IT dept? (I'm not aware of any other websites not working - just the stackexchange family using

Also, I can connect to, it just the cdn. subdomain

EDIT: Also, any reason why does not use the cdn?

EDIT: The issues appears to have resolved itself .. not sure who did what where...

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I'm also seeing the problem, in my office in the UK. Your office doesn't happen to use WebRoot Proxy as a filtering provider, does it? – Matt Gibson Jul 20 '11 at 10:19
On further investigation, my problem seems to be a DNS lookup: I get "DNS lookup for the web server name ( failed." if I try to visit the URL for one of the stylesheet directly. – Matt Gibson Jul 20 '11 at 10:22
@Matt: Yes, I believe we do have a WebRoot Proxy. - but the issue appears to have now resolved itself. – Grhm Jul 20 '11 at 10:43
I've found WebRoot proxy unreliable on DNS lookups on at least another couple of occasions this week (I think with their system it's their proxy server that does the DNS lookup, so I guess it's just a bit rubbish at the moment.) They also seem to be blocking all sorts of random things -- my image placeholders have started failing because they've blocked for "Media Sharing"! – Matt Gibson Jul 20 '11 at 10:48
@Bobby Those all appear to relate to failure of the CDN/connection to the CDN after a successful DNS lookup, rather than what I'm seeing. But I suppose that they're technically duplicate questions, even if the answer isn't the same... (Incidentally, I just temporarily hardcoded a CDN IP address in my hosts file, and it's working fine now, so it's definitely a DNS issue for me.) – Matt Gibson Jul 20 '11 at 10:57
This is still affecting me. Cannot connect to at all, so stackoverflow gets served with missing content. Some stuff is usable (can post a question) but some other functions don't work (cannot post comments). works fine. Maybe as a workaround, make changes necessary to have stackoverflow functional even without cdn served content? – user1394355 May 16 '12 at 13:51
C:\Windows\System32\drivers\etc>tracert Tracing route to [] over a maximum of 30 hops: 1 * * * Request timed out. 2 * * * Request timed out. ... until it gives up. – user1394355 May 16 '12 at 13:53
having similar issue. – Sisir Jun 13 '13 at 9:02
SO has been down for me for 10 days now. Considering the Google result for "jquery ajax error NaN" this can be called a catastrophe. I'm in Africa. I'm told SO was fine (on the speedy side) here for years. What happened on the 1st of august? – xaccrocheur Aug 6 '14 at 10:26
@xaccrocheur You might want to raise this as a separate question - it not going to be noticed as a comment here.. – Grhm Aug 6 '14 at 10:51
I get the same issue routinely when I'm on the company VPN & proxy. To answer @user1394355 I put entries for and in hosts (which I swap with Hosts Switcher when I drop/reattach to VPN) and downloaded all the files that SO needs to a separate web server that hosts now points to. That works, though at some point my files will fall out of step with SO's. Fiddler might be a less intrusive workaround than a heavy-handed hosts change/server stand-up. – ruffin Apr 30 '15 at 13:22
@Grhm If @xaccrocheur could get here but not SO, there's a good chance he's having the same issue you were. As you noted, Meta doesn't pull these files from Initially, I edited the cdn links in Firebug or Chrome's web tools so SO used Meta's (which made SO look a little funky). Then I found that, strangely, SO's CSS files are/were on meta too. Example:… Unfortunately that's a different path than SO wants, or I'd've pointed hosts to Meta! – ruffin Apr 30 '15 at 13:30
up vote 5 down vote accepted

Well, given that we both have the same problem and we both seem to be using WebRoot Proxy, I'd say that the issue is that WebRoot Proxy is having problems resolving the IP address for The DNS lookup error I see when I try to visit one of SO's stylesheets in my browser certainly seems to come from WebRoot Proxy's servers rather than anything local.

I've tested this by temporarily making a local override for one of the CDN's local IP addresses ( in my hosts file, and that has allowed me to successfully see Stack Overflow's stylesheets again.

The long-term solution is to get your IT people to get on to the providers of the WebRoot Proxy service and ask them nicely to investigate their DNS lookup failures, I'd say.

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I don't think my issue was WebRoot failing to do DNS lookups. The error message (as shown in my question) quoted the server name and IP address. – Grhm Jul 20 '11 at 11:08
@Grhm Good point! I hadn't noticed the IP address in your post. Interestingly, my problem seems to have disappeared now, though I've removed the IP address hardcoding and flushed my cache. I still suspect some transient problems at the proxy side of things are the cause for both of us... – Matt Gibson Jul 20 '11 at 16:18
@Matt Gibson i tried to ping it is not reachable Ip is returning. which is content provider for stackoverflow – bikram990 Jul 12 '13 at 10:34

I had this problem.

After digging into my firewall, I discovered that the IPv4 addresses for were on my bogons list. My firewall's bogon-blocking list had become out-of-date.

So, update your blocked-bogons list, or turn off bogon filtering in your firewall, and becomes reachable.

Team CYMRU maintains downloadable IPv4 and IPv6 bogon lists that can be loaded directly into a pf table.

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Four very similar answers in quick succession. Is this necessary? Is it legit? – Werner Nov 5 '15 at 5:06
@Werner: No and the system actually automatically flags carbon-copy answers posted in this manner. – BoltClock's a Unicorn Nov 5 '15 at 11:24
@Werner: Not intended as spam. Just read through several instances of the same problem here while trying to solve it. Posted my solution to each thread so others wouldn't have to dig as hard. If SE wants to merge them all together, that would be preferable. – Jason Stewart Nov 6 '15 at 6:08
@BoltClock'saUnicorn: Not intended as spam. Just read through several instances of the same problem here while trying to solve it. Posted my solution to each thread so others wouldn't have to dig as hard. If SE wants to merge them all together, that would be preferable. – Jason Stewart Nov 6 '15 at 6:15

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