![alt text][1]**My example 1:**

Let's suppose in the response is the string ''Frankfurt''.
We want to verify that the response 'does not contain' the string ''bob''

create a checkpoint on the field with Expected value like the following:
Regex ^((?!bob).)*$

This checkpoint will PASS if the response is ''Frankfurt'' because we are checking to make sure the response does not contain ''bob''

**My example 2:**

Let's suppose in the response is the string ''Frankfurt''.
We want to verify that the response 'does not contain' the string ''ank''

create a checkpoint on the field with Expected value like the following:
Regex ^((?!ank).)*$

This checkpoint will FAIL if the response is ''Frankfurt'' because we are checking to make sure the response does not contain ''ank'', but of course it does contain ''ank''.

Confusing enough?

[1]: /storage/temp/386-2016-01-08-1611.png