why flush dns?
Dns is short for Domain name service or domain name server ,when you type a url just like www.google.com in the address bar the browser will ask the dns what is the realipaddress of this domain www.google.com then your dns server will give you the real ip address of the domain .so that the browser could build a tcp connection to google’s server .
theare are a ot fo dns server around the world they copy the dns record from other dns server and send it own dns record to others this need 10mins to 24hours even 3days .so when you try to resolve a domain into ip you may get the wrong answer. that is not keypoint ,most of the time you comupter will cache the dns record for speed this is the real reason why you should flush dns . when you flush dns the computer will cleare the cache on your computer so when you try to use internet new dns request will sent to dns server again instead of use the cached record.