I'm noticing discrepancies between ads I'm paying for on Facebook and the matching Google Analytics to those pages.

Yesterday, I had an ad that FB told me was clicked on 4 times. Analytics shows 1 visit to the page that the ad links to. It's a deep link, not the home page.

Any idea why? Do I have to plant the analytics detection code on every page on my site or is planting it on index.html good for the whole site?

The only thing I can think of is that analytics is only picking up on visitors who come to the site through the index.html page and not folks who get in the back door.

Let me know what you think.