The primary purpose of the private browsing mode that all internet browsers offer is to a way to temporarily disable the logging of websites and specific web pages that are being viewed. It has other uses too. It prevents the various tracking systems that websites put in place that watch you move round the internet and monitor what you click on. Also, it's sometimes possible for a browser to get into a funny state and not show a website as it should be due to what it already has cached in its memory. The quickest way to confirm whether there's a genuine issue with a site or whether the problem is with your browser cache is to switch to private browsing mode and see if the problem persists.
Every browser provides a way of enabling this mode, although they all call it something slightly different. In general, it's a matter of activating the menu (usually in the top right) and looking for the word "private" somewhere, and clicking that. For more specific instructions, find the browser you use below for a screenshot showing where you can find the option.
How to open a private window in Google Chrome
Google call their private browsing mode "Incognito". To open an incognito window, click the menu in the top right of the browser and pick "New incognito window", or use the Ctrl, Shift + N keyboard shortcut.
How to open a private window in Microsoft Edge
Microsoft call their private browsing mode "InPrivate". To open an InPrvate window, click the menu in the top right of the browser and pick "New InPrivate window", or use the Ctrl, Shift + P keyboard shortcut.
How to open a private window in Apple Safari
To open a private window in Safari, open the file menu and pick "New Private window", or use the Shift, Command + N keyboard shortcut.
How to open a private window in Firefox
To open a private window in Firefox, open the menu in the top right of the browser and pick "New Private window", or use the Ctrl, Shift + P keyboard shortcut.
How to open a private window in Internet Explorer
Microsoft call their private browsing mode "InPrivate". To open an InPrvate window, click the cog in the top right of the browser and pick Safety, and then "InPrivate Browsing", or use the Ctrl, Shift + P keyboard shortcut.