How can I find out what version of macOS/OS X is on my computer?

The steps are the same for all versions of macOS and OS X. Click on the Apple in the top left corner of your screen. From the menu that appears click on About this Mac. A panel will appear in the middle of the screen showing the name and version number. A summary of all macOS versions can be found here.

How do I reload a web page when using any web browser on macOS?

Most web pages consist of multiple files and, in normal mode, all of these files must be loaded into cache (usually your computer's hard disk) before the web page can be displayed. The file name displayed in the URL is only one of those files. Sometimes, the web page you see may be out of date, because the data has been loaded from cache from the last time you accessed the web page, rather than from the web site itself. This is why you may need to refresh or reload some or all of the files in cache for that web page, to see the latest version. If you want to refresh/reload just the file shown in the URL: Click or press Command+R If any of the other files used by that web page have been changed they will not be reloaded, and the version already in cache will be re-used for them. This may not necessarily reflect the latest changes. If you want to refresh/reload all of the files associated with the web page you will need to do the following: Hold down Command and click or press Command+Shift+R If 'incognito mode' is used, browsing history is not retained, while all cache files and cookies are deleted automatically when the session is closed.