I work for a small agency doing Adwords. Occasionally help out some clients with basic SEO. 

We got an email from a client we have done some campaigns for in the past 

Client: You provided us SEO consultation when we launched our site, and now our traffic is decreasing. Please fix it. 

Although I had no idea exactly what we consulted them on, I did an audit of their metadata, links, and other information I could get without back-end access to figure out what could be causing the problem. 

Me: I’m not seeing anything wrong - could you provide me access to your Google Analytics so I can get a better idea where the drop is coming from?

A few days later, they email me back with the login information to look at their numbers. 

I logged on and immediately saw that their online traffic had grown around 30% from when they launched the site. 

The downturn they were noticing? It turns out people aren’t as interested in buying bathroom tiles in December. Every year going back to 2012 their site would have low visitor numbers during this month. Maybe because, I dunno, people tend to spend that money on gifts rather than home innovations in December? I know, crazy right?

The whole thing didn’t take too long to figure out, though I found it a little ridiculous that they specifically worded the email so it would sound like this was our fault because of some advice we gave them twelve months ago.

Source: Clients from Hell