Your desktop or laptop computer will store what is called DNS cache from each of the locations, websites, and IP addresses, you visit on the internet. This cached version of a website's DNS information allows computers to quickly recall recently visited websites, making the connection to those websites much faster. DNS cache is not updated or changed very often. In some cases, DNS records related to a website may go unchanged for years or even decades.
Where a problem will occur is when DNS records are updated or the location of a web server has changed for a domain name/website and the DNS cache in a computer reflects the old information. When this happens, the computer will no longer be able to connect with the website, causing an error to display in the browser. When a webmaster is configuring a new domain name or website, there is a high probability that this scenario could occur. If a webmaster who is unable to access their website does not realize their computer has outdated DNS cache, this could lead to hours and even days of frustration trying to figure out why their new website is down.
If a browser error is experienced while configuring a new domain name or website, one of the first points of diagnostics to be done is flushing the DNS cache from the local computer used to configure a new website or domain name.
Windows 10 Computers
Learn more about flushing DNS cache on Windows PCs from Microsoft Support.
MacOS 10.10 to 10.10.3
sudo discoveryutil mdnsflushcache
OS X Yosemite and later (v10.10.4 or later) use this command:
sudo killall -HUP mDNSResponder
Learn more about flushing Apple and Mac OS DNS Cache and MDNSFlushCache command.
Ubuntu Operating System
First, run the command:
sudo systemd-resolve --flush-caches
Then run this command:
sudo systemd-resolve --statistics
Learn more about flushing Ubuntu DNS cache and Systemd-Resolve.