(full disclosure: this is not the online sales graph for a winery)
What happened in December of 2009? The company involved started to make changes in their Web site, one at a time, measuring the changes.
Notice that I didn't say "they redesigned their entire Web site." And it was pretty horrible to start (and it's still no prize, in my opinion).
They just started with a pretty horrible design, and started removing the "rocks" that impeded customers from making a purchase. Turns out, they didn't have to remove too many.
You can read the full story here. If your site gets at least 50 visitors a day (which may be the first problem you need to solve), you can get the same treatment (for a price).
I apologize that this story isn't about a winery Web site, since that's what you come here to read about. But I think it's valuable because it talks about incremental changes guided by measurement, which applies to your winery Web site as much as it does to a site selling The Amazing Bible Timeline.