Try as I might I cannot at the moment load any Apple web page, either in the US or Australia, using either Safari or Firefox (which I occasionally engage when Safari splutters) on my late 2013 iMac OS 10.11.2

I’ve turned off ad blocking extensions (Ghostery, Scamzapper etc), tried various user agents in the Safari Develop menu and turned off Little Snitch network filter. The page loads about 25% of the progress bar but no content and then stops. No “safari cannot load page” dialog or anything. Non Apple sites are fine.

However I can load any Apple site with my iPhone or iPad via my normal WiFi network. Logically this all seems to point to some system setting/ blocking issue specific to my iMac. I’m now at my wits end (such as they are) and would be grateful for any advice…