> perhaps everyone's traffic spiked a bit on Dec 29th and 30th and it had nothing to do with the email blast we sent out You don't need any external knowledge

> perhaps everyone's traffic spiked a bit on Dec 29th and 30th and it had nothing to do with the email blast we sent out You don't need any external knowledge to resolve questions like that. You only need to tag the links in all your marketing campaigns, including "email blasts", so that you can identify the traffic from those campaigns in your web stats reports. To know whether a spike was caused by the e-mails or not, you just look at how many visits came from that campaign on the 29th/30th. Whatever analytics platform you choose should make it easy to see how many visits each traffic source is bringing you each day, so you can answer these questions you have about the causes of spikes and dips.