This sounds like a problem that the site administrator will need to fix. If it's not critical to gain immediate access, try again in an hour -- they might be in the process of updating something.

Edit: Just saw the URL and that site works normally for me at the moment. If it still doesn't work for you, try clearing your Firefox cache and deleting your saved cookies for the site.

1. Clear Firefox's Cache

Tools > Options > Advanced > Network > Offline Storage (Cache): "Clear Now"

2. If needed, delete the site's cookies

Tools > Options > Privacy > Cookies: "Show Cookies"

(That assumes you have custom history settings)

Carefully remove the site's cookies individually, do NOT click remove "all" unless you really want to remove all your cookies (there is no undo for this dialog).

Does that help?

Thanks for your prompt reply. Appreciate it. Tried clearing the cache and deleting the cookies but didn't work. Guess I'll wait for a while. Thanks

Does it help if you go to this addresss (no www): http://defensetech.org/

Unfortunately not

To see whether it is something specific to your add-ons or settings, you could try accessing the site using Firefox's Safe Mode.

First, make a backup of your computer for safekeeping. To back up Firefox, see Backing up your information.

Next, try starting Firefox in Firefox Safe Mode. Be careful not to "reset" anything permanently if you didn't back up.

Any luck?

No luck! I have a few cookie control and security add-ons (eg noscript, betterprivacy etc) so I suppose they might be interfering. Thanks for your help so far.