Skeleton is a prototyping tool, with focus on the layout and structure of your html document.
Skeleton is not a full-fledged prototyping tool. Not even close. And Skeleton is not just a visualisation tool.
Skeleton is a tool for amateur to beginner web-enthusiasts, for visualising a layout for their web-page. Not only that, you can create a layout of your choice, and then generate a document-markup, on the fly.
Normally for a person like me, a webpage starts on a piece of a paper. Sketch-by-sketch, the design improves and finalises. And I wanted something which could easily transform that design on the paper into a workable template. Hence the need for Skeleton. If I get time, I will work on making this tool useful in a practical situation.
As I mentioned before, (currently) this tool is for amateur to beginner web-enthusiasts.
Tested on latest builds of Chrome/FireFox/Safari.
Download the zipped code and (obviously) unzip it! Open up 'skeleton.html' in Chrome or Firefox. On the left hand side of the screen, you will see red, yellow and green blocks. They represent div, table and p tags respectively. Drag and resize these blocks, to suit your requirements. Once you are done, click the button and your markup will be generated. The unused blocks will not be accounted for. The algorithm takes care of nested blocks. And partially-overlapping blocks, are not treated as nested elements. The algorithm also takes into account the order, in which your blocks appear from top-to-bottom.
I hope Skeleton proves to be helpful to you.