1. Failure to properly institute server redirects
You’d be surprised to see how many websites still don’t 301 one version of their site (whether www or non-www) to the other version. This causes issues with indexation and link juice.
If you run both www and non-www versions without a 301, you’re essentially splitting the link juice, as people will link to you using both non-www and www paths. If you 301 one version and people link to the nonpreferred URL, you’re still getting the link juice benefit through the 301, so make sure you pick one or the other.
2. Internal link structure
From not using good anchors internally to wasting nav space on lower-quality pages, suboptimal internal link structure is one of the most common problems I encounter when reviewing a site. It’s a rare site that actually needs to link to 100 equally important pages from the homepage, but you wouldn’t know it to look at some sites.
I’ve seen that especially with e-commerce sites that sell niche items. It’s great that you have 100 types of products, but there’s a better way to get a user there than by having them all in a leftnav.
Additionally, I see lots of people wasting opportunities for good anchor text internally. If you’re linking to your metal posters page with the anchor “Ripped!” then you’re also potentially confusing users and squandering conversions.
3. Not making additional important features obvious to users
If you have a Twitter account, list it on the home page. The same goes for Facebook. I’ve looked at several sites recently and while they do have social media accounts, you’d never know it unless you happened to search for it.
The same holds true for a company blog, a YouTube channel, or anything else that will flesh out your online presence and give users more content and more opportunities to interact with you in different ways. Let people know where else you hang out.
4. Not using 404s properly
Different people like to handle 404s in different way. My agency just sends any page-not-found request back to the home page. Hey, so does The Onion!!
I thought this was the easiest route to take, but my preference would probably be a custom 404 scenario that did the whole “were you maybe looking for this instead?” list of URLs based on a semantic analysis of what was typed, along with a handy site search box and all old pages/potentially-mistyped-paths 301′d. I can dream can’t I?
Some people use very creative 404 pages. Some people 301 the heck out of every possible error URL you could dream up. The key is, indeed, to handle 404s and not just leave a user hanging.
If you have any links going to pages that are no longer found on your website and you aren’t handling this, that’s obviously a bad user experience — which leads to fewer conversions — so ideally you should make sure you 301 any old URLs that have inbound links.
If you only do a pretty 404 page, make sure that it contains a link to your home page at the very least, so you’ll still provide a better user experience.