The World Wide Web runs on a system of Domain Names (Domain Name System = DNS). These are the names we humans use to access websites like www.google.co.uk or www.goldhosts.com.
Computers however are much better at numbers than names. The "address system" for the internet is actually based on numbered addresses (eg. 188.8.131.52).
The DNS system of the internet uses Name Servers to translates the names we use into these numbers. The designers of this system built it in such a way that the "lookup" does not need to be done every time a name needs to be resolved, a "cached" or "remembered" version can be used for a specific period.
This "memory" effect means that when an address is changed, it can take up to 48 hours for the new address to be seen.
In reality, the changes can happen quite quickly. Sometimes almost immediately, depending on the quality of the settings on the Name Servers.
There is however a period of uncertainty, as it is possible that a cached result will be used by one network, while another network may have already used the new system.
This discrepancy we refer to as Propagation Time.
There are techniques which can minimise (to a lrage degree) the time propagation takes, and we can help if you need it. If you are concerned about changes you have been asked to make, call Goldhosts for expert help.