Visitors to your author website are precious. Whenever a reader takes time out of her day to seek us out, we want to make sure we're rewarding her with good content and few distractions.
Here is a short list of common sins and how to avoid them.
One: No Contact Information. When I take the time to make my way to an author's website, half the time it's because I'd like to say something nice. When I can't find any contact information, it makes me feel stabby. And maybe I'm old school, but when I say "contact information" I don't mean your Facebook page. A real email address is pretty important. If you're worried about the address being scraped for spam, you can write it like this: myname (at) gmail.com.
Yeah, spam is awful. But frustrating your reader is worse! I promise. Make yourself available, so we can say nice things to you.
Two: Where's Your Newest Book? Another top reason I visit your site is to see what's new. And if the new thing isn't immediately visible on your home page, I'm probably going to assume that you don't have anything new! In the immortal words of Paul Simon, I "got a short little span of attention." So don't make me look too hard.
Three: Your Reader's Phone Makes a Mess of Your Site. About 50% of web traffic to author sites comes from mobile devices. If your site doesn't play nicely with mobile browsing, your visitors might not make a second visit. Make sure you test your site on a couple different devices to see how it looks. The days of building "a website" are over. Now a web designer builds a thousand possibilities at once, on every page. Also, Google promotes mobile-friendly sites to the top of its search ranks. Make sure your site isn't frustrating 50% of your viewers, just because they showed up on an iPad.
Four: Music and Animations. A sudden soundtrack might be the last thing a visitor needs if she's checking out your site while sitting on a bus or in a library. And gimmicky tracks and unnecessary video slow down web connections, making it tougher for your reader to find the content she wants.
Five: Intellectual Property That's Not Yours. I know it's fun to use celebrity memes and droolworthy photos, but it's a bad idea. There are legitimate (and illegitimate) cases brought against authors and bloggers all the time for photo copyright infringement. At best it's a headache and at the worst it's an expensive headache. So make sure you use photos you own or which are licensed by the creator for free use. Trouble is no fun!
There are other sins of author websites, but these are at the top of my list. What's at the top of yours?