iMac being blocked from website on all browsers

Your issue is likely caused by Avast. Mac OS is extremely secure and does not benefit from nor does it require ANY third party antivirus, cleaning or any other types of "maintenance" apps. Most have the exact opposite effects that users want, they make their Mac slow and unstable and exhibit behavior similar to what you are experiencing. All Mac OS needs to remain stable is to be kept up-to-date and otherwise left alone.

Please post a EtreCheck report of your system and we can then look for any other issues due to what has been installed on the computer.

Please locate the uninstall instructions for Avast (and any other similar products as described above) and please uninstall. dialabrain is 100% correct, please follow the advice. If you don't want to, that's okay but there is not anything we can do to assist.

See if it works in Safe Mode.

Use safe mode to isolate issues with your Mac - Apple Support

FWIW, the site works fine here and, you should uninstall whatever AV program you have installed.

Did you delete just the Avast app or all of its supporting files, i.e. did you use the developer's instructions.

If not then you can check to see if you've removed all of the files by downloading and running Find Any File to search for any files with the application's name  and the developer's name in the file name.  For example for Avast software you'd do the following search: 

1 - Name contains avast`

Any files that are found can be dragged from the search results window to the Desktop or Trash bin in the Dock for deletion.

FAF can search areas that Spotlight can't like invisible folders, system folders and packages.

Please post the previously-requested EtreCheck data. Download and run thar, open a new reply here, press the button that looks like a printed page to get a text input box big enough to paste the hardware and software configuration report here.

I’d encourage an upgrade to macOS 10.13, too.

Add-on anti-malware is arguably intentionally-installed malware that just doesn't like to share, this given how it ties into a system, and also given revelations around anti-malware data collection.

Have you tried another browser?

Also, create a new user on your Mac, log out and then log into

that user and try accessing the site.

Well, Macs do not need antivirus apps. Not only Avast but others. Avast was recently caught collecting…

"Using dev tools to examine network traffic, Palant was able to determine

that the extensions were collecting an alarming amount of data about

users’ browsing history and activity, including URLs, where you

navigated from, whether the page was visited in the past, the version of

browser you’re using, country code, and, if the Avast Antivirus is

installed, the OS version of your device, among other data. Palant

argued the data collection far exceeded what was necessary for the

extensions to perform their basic jobs."

I'm not terribly surprised the problem you are having. Frequently using antivirus apps make such a mess for a user that they are forced to do an erase and install and start all over. They can use their backup to restore just the data files but should install all of their apps manually.

Yes. They've been having that problem on and off for a few days now.

woodmeister50 wrote:

Have you tried another browser?

"The same issue happens in all browsers"

Rhetorical question? 😎