A hallmark of stylish, modern websites seems to be the visual effect that uses a background image with text that scrolls over the image. When you scroll through what is usually a lengthy Welcome page, the background image scrolls more slowly than the text (scrolling in parallel, but more slowly). This effect is known as "Parallax Scrolling" and Squarespace offers a number of templates that use it.
Weebly, the other website design platform I use most often, offers page sections that allow you to put a background image on the page and then have text scroll over it. It isn't true Parallax Scrolling because the background image doesn't move, but judging by the excitement in the Weebly Designer community when sections were introduced last fall, designers are eager to try out this new feature.
I personally prefer a cleaner, shorter Welcome page without a lot of movement and a lot of scrolling. So far, none of my clients have chosen the scrolling effect either, so I'm compiling a list of Squarespace templates that don't use Parallax Scrolling to help new clients narrow down their preferred template choices more quickly.