MAMA

Behold the coming of our MAMA! MAMA (Metadata Analysis and Mining Application) is Opera's structural search engine; whereas normal search engines return results about the content of pages, MAMA returns results about site structure, including what doctype the page uses, whether it validates, what HTML elements and CSS properties it uses, what plugins, what scriping constructs, and much more. This is an invaluable tool for many individuals and companies involved in our industry, and Opera wants to share it with everyone. Read on to find out more about it.

( Read the article )

The billion dollar secret of valid HTML (XML/SGML/any CODE) is easy reusability of content in the process of conversions without errors, retyping, reformatting and reworking: html2pdf, html2doc, html2txt,html2latex,html2ps or whatever format without any effort and magic.
And imho, "write once valid htmlcode and run it everywhere"

$GML/HTML, the billion dollar secret, how some of the world leading companies are turning documents into assets and saving billions of dollars..................
http://www.amazon.com/SGML-Billion-Goldfarb-Information-Management/dp/0132267055/ref=sr_1_4?ie=UTF8&s=books&qid=1224190900&sr=8-4

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KompoZer is a complete web authoring system that combines web file management and easy-to-use WYSIWYG web page editing.

I have already spent some time expermenting with Opera's MAMA and I must admit that is a really great feature. I would also like to thank for the series of excellent articles about MAMA with regards to various HTML element.

The release of Opera’s MAMA is a really spectacular news. For quite some time I’ve been in desperate need for an efficient structural search engine and this one seems to meet all my requirements. I hope to see the future development of this great tool.

I'm currently playing with some structural search engines right now and MAMA is a very interesting solution. Great work with this tool and keep developing it! Also the series of MAMA tutorials allows for a smooth acquisition of all necessary knowledge to use this great tool.

Something in this direction i'd be interested in for finding examples (next to just reading all of dev.opera.com of course)
MAMA: list me valid webpages containing <h1>, <span>,
<style="background-image:url('*.svg')"> <circle> doing AJAX