You may call this as a hack or a trick or a bug in gmail.If you have a gmail ID then you can create and use multiple email ID’s with the single gmail ID .So, there is no need to create different email accounts for registering multiple times on a single website.Suppose ,I want to create two accounts on abc.com then I have to use different email id’s for each account but with this method I will be able to register on any site multiple times with single email account.I have tested this trick on gmail account but have not tried it on Yahoo or Hotmail.So the Requirement for this trick to work is
You should have a gmail account
Here is the step by step tutorial on Trick To Use Multiple Email ID’s From Single Gmail Account
The basic idea behind this trick is that websites treat email Id with .(dots) or +(Plus) to different whereas gmail considers them same.