A web cache is a mechanism for the temporary storage (caching) of web documents, such as HTML pages and images, to reduce bandwidth usage, server load, and perceived lag.
What is a web cache?
A web cache stores copies of documents passing through it; subsequent requests may be satisfied from the cache if certain conditions are met.
Find out more on Wikipedia: http://en.wikipedia.org/wiki/Web_cache
How to clear your cache - Chrome
Open the settings on Chrome. Click the menu icon in the upper right corner of the browser to the right. Click settings on the bottom of the menu.
PC: press Control + Shift + Delete
Mac: press Shift + Command + Delete.
Click "Show advanced settings"
Select "Clear browsing data"
Choose "the beginning of time" from the Obliterate the following items from line and tick the "Empty the cache" box.
Press the "Clear browsing data" button and you're done!
How to clear your cache - Internet Explorer (IE) 8 or higher
Once your browser is open, click the gear icon at the top right to open the Settings menu. Then, select Safety and Delete Browsing History....
You can also click Tools and select Delete Browsing History, if you have a menu bar.
Or, alternately, you may simply press Ctrl + Shift + Delete to open the Delete Browsing History window.
Select Temporary Internet Files. You will also need to uncheck all of the other boxes, especially Preserve Favorites website data.
This option makes the window also delete objects from websites in your Favorites folder, which is necessary to completely clear your cache.
Click the delete button
How to clear your cache - Mozilla Firefox
On a PC, click the "Firefox" menu in the top left corner. Next, select the right arrow next to "History >", and click "Clear Recent History"
On a Mac, from the Tools menu, select "Clear Recent History…"
Make sure "Details" is expanded, then select "Cache" from the list. Uncheck everything else.
In the "Time Range to Clear" drop down, select "Everything".