COOKIES - WHAT THEY DO AND WHY/WHEN TO DELETE THEM
Cookies are a tool that websites use to (a) speed up your web browsing and (b) help them give you a more personal experience with their website.
Cookies are small text files generated by a website detailing where you went and what you clicked on their website. The cookies get stored on your computer in a special folder for your web browser. When you visit their site again, they can check your computer for their cookie file to find out what you did the last time. Then they can change their website to give you a personalized experience. They may also store any information you typed into their site so you won't have to type it again on subsequent visits.
While cookies are no doubt helpful to your shopping experience, they are also a security risk given all the information they store for you.
Cookies are one part of your "Browsing History". Your browsing history also includes websites visited, downloads, form and search data, site preferences and cache. This is basically a stored version of everywhere you go and everything you do online.
The tricky part is that you cannot just "turn off cookies" or many websites will not allow you access. They require their ability to create and place cookies for your visits. So while you generally have to allow cookies, you can delete stored cookies and other browsing history data at any time.
WHY DELETE COOKIES AND BROWSING DATA
(1) If you are using a public computer, or computer other than your own, you will probably want to remove these files -- especially if you typed any personal information.
(2) Cookies and browsing history files build up over time and eventually slow your browser performance down because they have too many files to go through before they load page content.
(3) These files could be a security risk should a malware program get on your computer and capture this data. Browsing history data is not really "encrypted" so if found, it is readable and usable.
(4) It is a little disconcerting, to say the least, to know that "companies" out there know where you've been, what you've searched for, what you've clicked on, and more. To know they have access to this information for themselves or anyone they wish to share it will ought to unnerve us at least a little.
(5) Cookie data can be an issue if any cookie data is corrupted or if a website changes its cookie format or has a bug, keeping it from opening/reading old cookies. It is not uncommon to be unable to view or log into a website because of an old cookie.
(6) Lastly, if YOU change your information (your address, preferences on their website, login information, etc.), you may need to delete your cookies and browsing data before it allows/accepts your new data. (it will keep auto-entering old data)
WHEN TO DELETE COOKIES AND BROWSING DATA
There is no set rule here. It is common to delete them periodically (every month, or 3 months, or 12 months) just to kinda clean things out as well as whenever it is needed --- for example if a web page is not refreshing or if you have just been shopping/browsing online and you wish to remove the record. Cookies and browsing data do not take up very much space so you shouldn't be concerned about your hard drive getting filled with cookies or browsing data.
HOW TO DELETE COOKIES AND BROWSING DATA
Internet Explorer
Click the Tools gear in the upper right
Click Internet Options from the menu
Click Delete Files from the section in the middle on browsing history
Click OK after the list of all it plans to delete
Google Chrome
Click the three vertical dots in the upper right corner
Click Settings from the list
Scroll down and click Advanced
Scroll down the first section and click on Clear browsing data
Choose the time frame at the top and click Clear Browsing Data
Mozilla Firefox
Click the Menu button, then Library, then History
Click Clear Recent History
Set Time range to clear to Everything
Click on the arrow next to Details to expand the list
Select Cookies and make sure items you want to keep are not selected
Click Clear Now
Safari (Apple iPad or iPhone)
Find and touch the Settings icon on a main screen
Scroll down and touch Safari on the left
Scroll down and touch Clear History and Website Data on the right
Touch Clear