Why we clear our cache:
Each time you access a file through your web browser (Internet Explorer, Firefox, Chrome, etc), the browser caches (i.e., stores) it so it doesn't have to keep retrieving the same files or images from the remote web site each time you click Back or Forward. You should periodically clear the cache to allow your browser to function more efficiently and correct for errors.
A cookie is a file created by a web browser, at the request of a web site, that is stored on a computer. These files typically store user-specific information such as selections in a form, shopping cart contents, or authentication data. Browsers will normally clear cookies that reach a certain age, but clearing them manually may solve problems with web sites or your browser.
Either of these files can become corrupted or out of date before the browser automatically removes them. This can happen due to an update made to a website or simply from encountering an error when creating the cache file itself. Clearing the cache is a good first step that can resolve errors and narrow down root cause.