What is DNS - DNS stands for DOMAIN NAME SERVER. DNS translates the websites name IP address.Ones your computer finds the wewsite's IP address, it's shorted into your DNS Web Cache.
How to flush DNS cache -
Changing DNS server can sometime improve internet speed.
If you want to remove junk files in your computer you have to fallow some simple steps:-
* Click on start button now you gonna go on all programs, click on Accessories
* In Accessories Right click on command prompt and click on run as a administrator that make sure you flush your DNS in command goes through
* In command prompt just type ipconfig /flushdns and hit enter 
* And now you see on screen successfully flushed the DNS resolver cache.