Is OSX/Safari update (21st March16) a help or a hazard?

Presumably, you're not using any Extensions? And you're not using any third-party anti-malware of any kind? These alone can give rise to problems with Safari.

Have you reported your findings to Apple (see the URL I quoted)? I urge all dissatisfied Safari users to do so, as otherwise things'll stay as they are.

Those have been tried weeks and weeks ago. None of them have been of any use.

I don't have or use any unsupported add-ons or extensions. Neither do I run any antimalware that could foul things up. I don't visit weird, dodgy websites; I generally keep to popular, well-vetted sites. I've always run a pretty clean machine, and yet Safari has been awful since around mid-February.

The question has to be asked 'Why is it that so many users are reporting very similar problems with Safari and yet you, apparently, have none?'

Do you perform your OSX/Safari/other updates manually, or do you just let them happen in the background each time? Have been wondering whether any differences in code on a given machine might result if the order in which updates were applied were different to those intended by the Apple developers. Have also been wondering whether the developers have in recent months checked that ALL changes to OSX/Safari work consistently on all three of the latest versions of OSX (and not just on El Capitan). After all, some of these malfunctions come and go.

Yeh, as far as I'm concerned, I've done all the right things, obeyed all the sensible rules, kept my nose clean, and yet am plagued with a permanent Safari problem. A dreadful advert for Apple, IMO.

Glad to hear you're getting somewhere with it.

I don't use wi-fi myself; my router's permanently connected via wired Ethernet, ruling out all issues related to wireless connectivity.

"...... so for now I seem to be fully resolved and running fine."

Are you absolutely sure of that? Try navigating around amazon.co.uk or amazon.com for, say, 30 mins, and see if you experience the ubiquitous freezing.

I find the comments from the Apple techies who assisted you very, very unconvincing. Why on earth would rebooting or resetting my router have any effect on what is essentially a browser software problem? A router doesn't function at that level; the router passes internet packets transparently, it's not aware of which browser you're using. And anyway, how is that it's just amazon and one or two other websites where the issue occurs? All other websites are fine, so it's not a general DNS resolution problem or anything of that kind.

As for resetting the SMC and/or the NVRAM, I think Apple just trot that one out when they're lost for any other explanation. All I can say is that, if they happen to be correct about the SMC, etc., then an awful lot of people are having pretty much the self same issue, and all simultaneously! And that includes people using other browsers and other platforms!

I'm sure there'll be very many other Mac users in these forums who'll echo my thoughts on this response by Apple. Are Apple seriously suggesting that, for those of us afflicted by the freezing and beachballing, the cause is our various networks and/or our routers? Absolute tosh!

I've long ago tried some of those things. However, I think it unnecessary to uninstall the two apps I use; they're popular and highly reliable apps and would involve a considerable amount of work to reinstate; there are limits to what I'm prepared to do. In any event, I think you're forgetting that Activity Monitor has identified the problem as being one that involves the browser and website. As I keep pointing out, the problem that I have isn't there if I keep to a Safari fontsize of 14 or less. Go figure. The AM report, and the evidence generally, points to an incompatibility issue of the browser with the website. I can't see how anyone could argue otherwise. Of course, with other people's experiences there may be other factors involved. Mine fortunately isn't that catastrophic - at least, not yet - and by using the aforementioned workaround I can browse okay and very rarely encounter the beachball, and then only momentarily.

I've taken a closer look at Apple's description of the main changes made to Safari with the update of 21st March. If you normally do the updates manually, you can see a few details prior to performing the download(s) by doing Apple icon > Software Update, waiting for the Apps Store to respond, and then clicking on 'More' when the individual available updates are shown.

Interestingly, for 21st March, the changes to Safari are, apparently:

1. An updated version of WebKit with enhanced support for images and CSS.

2. Improvements to the reliability and performance of Web Inspector.

3. Prevention of Javascript dialogs from blocking access to other webpages.

Perhaps this does represent some addressing of the recent issues with Safari that so many people have been experiencing?

To date, I've never known what WebKit is all about, but according to Wikipedia:

"WebKit is a layout engine software component for rendering webpages in web browsers. It powers Apple's Safari web browser, and a fork of the project is used by Chromium-based browsers, such as Google Chrome and Opera".

All of this looks relevant, I must say.