It’s astonishing how many third-party websites – directories, news sites, even sites running your banner ads – think they can just make up traffic figures, and you’ll believe them.
“Er, we have a special link format which your Google Analytics won’t record”. Do me a favour.
Assuming you do have Google Analytics or something similar on your site, and it says that website X sent you 3 people last month, then guess what? Website X sent you 3 people last month. And you must base your assessment of those sites on your numbers. When a desperate advertising salesman says his website generated 100 clickthroughs for you, and your stats say it was only 10, don’t doubt your stats. At best his systems are giving him inflated data, and at worst he’s just lying. Either way, you shouldn’t be doing business with him. Walk away, now.