Very limited
They try to hide bad technology development with words about effective web design. I ran into bug after bug then design limitation after design limitation. For example, their gallery for one page is limited to 9 images. They made this a hard limit. They also will not allow any image to be a link. They gave a really lame explanation about web design and security. This explanation is simply an attempt to cover lazy or bad (or both) application design. Maybe a very simple web site (that would never need to be "understood by google") could be created, but if you want to use any number of standard web features or techniques then you will be dead in the water. There are far better tools - Weebly for one - that are just as easy to use.
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SimDif — Website Builder, v1.89