This question seems to come up daily. The answer given is that Safari is installed as part of the operating system. Normally it cannot be individually upgraded. It is periodically updated when the computer's operating system is updated or upgraded. What happens is that web site engineers write their software to work with specific browsers and specific versions of them. The alternative is that you can use another browser that does work, such as Firefox or Chrome. Also, they can be individually upgraded. If you do update your operating system, that does not guarantee that Safari will be compliant with the site’s software. I hope this is helpful.