What are reasons some people can't access a website while most others can?

Question

I have a .NET MVC 3 Website hosted on a Server 2008 r2 VPS. The site only uses SSL 3.0 connections, so if you connect using HTTP it will bump you up to HTTPS. The site is for a small company, just for staff to check messages, etc. but for some reason a couple employees and one sister company are unable to access it. The DNS records were set months ago, and most people have never had a problem.

I had heard that IE may have some issues accessing secure pages so to check if this was the problem I made one page non-secure and sent out the link and they were still unable to access it. I also connected to random proxies trying to see if they would have an issue and had no problems.

The business that can't access it uses Internet Explorer (I don't know what version) and the IT department said it was not being blocked on their end. I don't know what browser the people who can't access it are using.

I'm in the process of getting more information as to what exactly the error people are having, but I thought I mine as well ask here for some common things to check, or what you think it may be. Is there any DNS stuff to check, I have both an A record and AAAA, the only thing weird is that the name server fields are blank and it won't let me change that (perhaps this has something to do with the domain being bought via Google Apps originally.) I can't think of anything else to try.

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Update

The reason a few people weren't able to get to the site was their own firewall or security settings etc., and these have now been fixed.

However the business that still can't get on may have a different problem: on Internet Explorer if they enter the URL and press enter, they get the busy icon for a long period of time (I don't know how long but would assume over 30 second or more) then it redirects them the Bing and searches for the domain name.

I don't know what the problem is, but I have a meeting with their IT department later this week. My guess would be some third party add-on or malware is redirecting them.

Answer 1

It's really very hard to suggest anything without more information, the nameserver thing is weird but not unheard of in the messy world of DNS. If I had to guess I'd say it's something local rather than your site.

The most common cause I've seen for this kind of thing is the adblock plugin, cached DNS information or overactive antivirus/antimalware. I'd advise doing four things:-

1. Get the users to launch an InPrivate session in IE and test again, this will rule out plugins, toolbars and the like.
2. Clear the windows DNS Cache, cookies, browser cache and all other saved website data.
3. Check for weird entries in the computers hosts file, there could be an old entry redirecting the site.
4. Check for sites blocked by local or network antivirus/antimalware, the users could have seen an alert and hit the wrong button.

Report back and let us know what happens!