What happens when a user asks for a page on your Web site that doesn't exist? Technically, the Web server returns a 404 status code to your browser, which means Not Found (according to the HTTP specification that governs exchanges between your browser and a Web server).
In many cases, you get the Web server's default 404 page, like this 404 from Kendall-Jackson:
It's kind of boring, isn't it? Here's an example of a much more interesting (and amusing) 404 page from Twisted Oak:
Does this sort of detail matter? I think so. Which one would you rather encounter? Even if you're not as twisted as Jeff Stai (I mean that in a good way, Jeff!), you shouldn't leave it up to someone else to decide what your visitor is going to see when something goes amiss.
You should periodically check your server logs and/or analytics reports to see what 404 errors are generated by your site - people may be accessing outdated/incorrect links from other sites, which your webmaster can automatically redirect to the appropriate page. People may also be consistently misspelling a page URL, which again, you can silently fix for them.
What do visitors to your winery Web site see when a page isn't found? You can test for yourself by going to www.YourDomainGoesHere.com/unlikelypagename.html and seeing what happens.