Does your traffic fluctuate noticeably? Are you not sure why it's happening? Do sudden drops in your traffic cost you money?

If so, you might want to consider a recent post by Problogger. Even though Darren Rowse (the Problogger) blogs mostly about, well, blogging, he nonetheless offers 6 clues as to what the cause of an increase or decrease in traffic might be, and what you can do about it:

1. Seasonal Traffic: most niches experience ups and downs that are completely natural, but you might want to isolate what you can do to capitalize on the highs, and bolster the lows.
2. Topical Interest: trends and events are going to stimulate public interest in certain niches, and while you should try to anticipate these trends/events, you should also have a plan for retaining these users after the fad is over.
3. Posting Frequency: Google likes frequently updated sites, so perhaps your site isn't being updated often enough -- you might want to try adding a blog to it
4. Shifts in Search Rankings: sometimes search engines change their algorithms and sites can lose from their rankings for no apparent reason, but as long as you follow Google's webmaster guidelines, nothing drastic should happen to your site's ranking.
5. Poor Quality Content: if your content is relevant to users, they're not going to come back or link to it, and you're not going to rank well on Google, so try to keep your content relevant to your target market.
6. Promotional Activities: just cause you build it, doesn't mean that they'll come, so a change in your marketing can have a big effect on your traffic; so try different things like using social media sites like Twitter to find users, leaving comments on other blogs and forums, or doing press releases.

Problogger's post was targeted mainly at bloggers, but Darren is also an very experienced marketer, so his advice is worth considering if you're trying to understand why your traffic is declining. So check out the original post, because Darren goes into much more detail about these potential causes, and has many more suggestions about what you do about them.