A lot happens when someone types in, or clicks on, your URL. Every element takes time, the milliseconds add up to seconds, and after a few too many seconds, someone who had a degree of interest in your work has already gone somewhere else.
Are you familiar with Kiva.org? It's a very progressive and cool micro-lending site. You can lend $20 to a girl in India so she can buy a cow and sell milk. Your micro loan can change someone's life. And Kiva.org's loan repayment rate is far higher than the big banks with their big loans. What a great story!
Any idea who Kiva.org's biggest competitor is? It's Zynga. Know what they do? They make games, many of which integrate with Facebook, like Farmville.
What's Zynga got to do with Kiva.org? Well, mostly nothing. Except that when someone has 15 minutes between work and dinner, they can probably only do one thing online. They might go to Kiva.org and loan that girl the money to buy her cow. Or they might just play Farmville. Or Angry Birds. In a busy world, you can't do it all.
The point, for those of us making Artists' Websites, is that even when someone is interested in your work, it's usually not an absolute interest. Ours is a time of abundance. Abundance is a better problem to have than scarcity, but at least we were designed for scarcity, anatomically and cognitively, we really have no clue how to handle the problem of abundance. This manifests itself with RealityTV shows like Hoarders, with peeps who meant to make a loan on Kiva.org but got sidetracked on Farmville, and also with peeps who tried to visit your website, but gave up when it took too long to load. Or when the navigation was too confusing to follow.
There are lots of page load timing tools online. Pingdom is a pretty good one:
Use it to check and to compare. You can type in any URL: your own, or any other site you're curious about. Check a bunch of artist's websites and see how their load times compare. They will probably vary widely. Some will be sort of quick, others will be pretty slow.
You should also check different platforms. Is Squarespace slower or faster than Wix? Many platforms are freemium. That's a business model where they offer you basic service for free, and give you the option of paying for various upgrades. You could put together a simple home page on several freemium platforms, and see how load times compare. You should also compare the load times of different themes or templates on any platform you like. Not only might Squarespace or Wix load faster, but one theme or look on the same platform might load faster or slower.
If you find a really beautiful theme that takes 6 seconds to load, and a less inspiring theme that takes 2 seconds to load... well... that's a tough choice. Your work might be better served by the faster loading platform+theme.