If I can generally reach web pages on the Internet but can't reach a specific one, how do I troubleshoot what the cause is as an end user?
Maybe the website is actually down.
Try visiting http://downforeveryoneorjustme.com.
If it says "It's not just you" the website is likely having an outage and you should try to report it if possible -- or just wait.
Maybe it's a DNS problem.
See if the website DNS name (let's say it is
If you get an "unknown host" error this means there is likely a DNS problem. You can try seeing if it resolves against Google's DNS with
If it does resolve with that command then you probably want to contact your DNS provider (likely your ISP). If you want to run further DNS tests, try GRC's DNS Benchmark for Windows, or the services just-ping.com and whatsmydns.net.
Maybe it's a browser problem.
If it does resolve in DNS, but you don't get ping replies it means they are either filtering pings or you can't reach that site. If you are getting replies you might have a browser or browser proxy issue. Try installing another web browser with all default settings and see if you get any different results.
Maybe it's a problem with your internet connection.
If it is resolving but you can't reach it try running
You can also try PingPlotter (Shareware; Free 30-day evaluation.) which will repeatedly run a traceroute and graph the results, so you can see if you have packet loss or bandwidth problems at any hop on the traceroute.
Let this run for a while. If it is timing out after only an entry or two you probably want to contact your internet service provider. If it is timing out towards the end you should contact the webmaster of the site, if possible. Whoever you contact, include the output of the
Something else to look for is a faulty router.
I recently had this situation with accessing any Stack Exchange site. It would time out, return connection errors and generally "lock me out" for 5 minutes at a time. Virtually all other sites were OK.
After lengthy chats with Stack Exchange staff (very helpful) and my ISP I narrowed it down to the router. Swapping it out has apparently cured the problem.
The problem here (I think) was that what ever the fault was on the router it couldn't cope with the relatively high volume of traffic I was generating when using Stack Exchange as a logged in user with multiple accounts and having a lot of them visible at any one time.
The fact that only one site (well one set of sites) was affected led me to believe that the problem lie elsewhere.
These days one needs to consider IPv6. It's possible there is a problem with the IPv6 mechanism (DNS, routing, OS) but not IPv4 (or, less likely, vice versa). Both the
This feels like a comment to the main answer, not another answer, but I don't have enough rep to comment. Or perhaps I should edit the Wiki, which would mean perhaps adding an example, since the answer is so professional looking. But I don't have enough rep for Wiki editing either.
Feel free to edit this as necessary.