Prop .. Propagation What?

What is domain name propagation? For new domain name propagation is a period where you newly registered domain being sent to all name servers (or DNS servers) in the world.

Hosting Migration
Hosting Migration

DNS server caches of your domain name mapping to IP address. This mapping record normally stored for time period to prevent querying or lookups. For example www.datakl.com resolves to 210.48.148.207 and stores in DNS servers around the world for 6 hours.

DNS servers drop stale DNS record based on few factors such as DNS record timing setting and
the practice of flushing records every interval period (normally ISPs)

Your computer stores DNS record for faster browsing to eliminate frequent DNS query to DNS servers.
The caching is beneficial for faster browsing but if you are in the midst of change hosting company or server, this process could cause confusion or downtime. Why confusion? In hosting or computing everything is almost instantaneous – upload your html/php coded page you can view instantly but for DNS the only solution is to wait!

On and off explains (After changing name servers I could view my web site for a moment and later turns to page could not be found or referring me back to old hosting server why?)

Normally your computer or router/modem use two DNS servers or more. The first (on) probably responded by a DNS server which has your newly modified record and the (off) page could not be found now could cause by another DNS server that still keeping your old DNS record -(error page could not be found or returning you to your old hosting company)

Just wait for propagation period to compete – normally 48 hours and your web site will resolve properly. Try on your luck by rebooting your computer – normally rebooting will flush the old DNS record in your computer or use ipconfig/flush command if you are using Windows DOS prompt. To have less impact on your operation or visitors, change your DNS during non busy hours is recommended – after office hours.