This is one analytics tip to keep. Given the time lag in the Google Analytic and AdWords universe the following picture would be falsely mistaken at first as a failure of either system. I tend to think that AdWords is more unreliable compared to Analytics, but recently I have opposite signs
Anyway, thinking bigger here should tell you the following, clicks are recorded in the Google system and reported in the AdWords suite while visits are recorded upon someone reaches your site. Boom! You got it, something might be wrong with your servers or a specific part of your site categories that serve as landing pages and you don’t have a clue until now. Now, make the math and calculate the loss you will be suffering in a similar situation if you are running large scale PPC activity…
How to diagnose this?
Normally you will monitor your Paid traffic on an daily level comparing hour to hour to another day (say last day or last day of the week). All thing equal traffic should not show signs like the graph above, ie scaled down from a certain time point and on. Then it’s time to look your clicks (either from Day parts or from Dimesions>Hour in AdWords GUI)