Authoring tools for HTML5 and “Google Web Designer” is?

Google Web Designer beta is a HTML5 authoring tool provided by Google.
Compared to other similar products, it is made for designing online ads.
If you use GWD, you can design with GUI like paint soft.
In CSS pain, you can edit style like developer tool.
It also has function to change code view, to edit HTML document, and to edit animation.
Yet beta version, but it is so much valuable to use for free.

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