Cannot Open Certain Web Sites

So I got a new computer recently (with Windows Vista) and started using Firefox. However, I’ve noticed that many web sites just won’t open. I get an error with Firefox, an “unavailable” message with Internet Explorer, and a blank window with Opera. All of which leads to me conclude that it’s something to do with my computer.

But it’s not internet connectivity problems, since I can access other web sites at the same time. And I doubt it has anything to do with my firewall, since these aren’t web sites that would cause alerts to pop up.

Any ideas, guys?


The sites that won’t open, do they have anything in common?

Which websites?

I don’t think so.

Pretty random. I can’t remember them all but two examples that come to mind are the pubmed site ( PubMed ) and

Try going to; this is the IP address that resolves to for me. If you can access the MTA website that way, but not through, the problem probably lies with whatever DNS server you are using, which is likely provided by your ISP. If that’s the case, it’s likely a transient issue that will fix itself soon-ish, though you could complain to your ISP if you want to.

Check your Hosts file to see if any of the bad sites appear. Delete and save as needed.

On my Win XP computer, the hosts file is here:

Nope, can’t access it. Plus, other computers in the house have no trouble accessing these web sites.

Hmm. I did that and opened the hosts file in notepad. This is all that appears:

have you disabled any/all security/virus software?

This has happened to me several times in the past, usually after installing some driver update or other, or after changing a bit of networking hardware.

In my case, it was the MTU setting on either the network interface, or the router - this governs the maximum size of a data packet and if it’s set just a little bit too high, it can result in certain sites not being available, while others are fine.

Google MTU settings and you might find something useful.

I’ve seen this and usually the easiest way to resolve the issue is to just reinstall the browser.

First get revo uninstaller. It’s totally free and it uninstalls all the leftover things most uninstallers leave behind.

Get rid of all the browsers using this. Go for the advanced uninstall and get rid of the program, the registry entries and the leftover files. (The program walks you through this, choose advanced uninstall)

Then reboot and install browswer again.

For IE8, you can’t uninstall it, so do this:

Go to tools (At top of page)

Internet Options ->Advanced (tab)

Then “reset” (about 2/3 of the way down). Note this will erase all your booksmarks and retore IE to scratch, so you will have to put on any “add-ons” you used.

A lot of things can cause said behaviour from inproper installs to incorrect or icompleted downloads you then installed.

Thanks guys, these sound promising.