Did you ask you mam in childhood about nature of things? Yeah, who did not..
And now Opera software [http://en.wikipedia.org/wiki/Opera_Software] presented MAMA – the Metadata Analysis and Mining Application. It is analytical search engine that returns details of page structure.

How can we use use it?

“We at Opera believe this tool can also be useful to other stakeholders in the standards and browser-making world.
For example:
Browser manufacturers and others can use MAMA data on the popularity of widely used technologies to prioritize bugs and justify adding support for new technology to in-progress releases.
Standards bodies can use the data to measure the success and adoption rates of various technologies.
Web developers can use the same data to justify support of various technologies in their work.
It can provide real-world, practical samples of the Web developer’s “art”, for inspiration and instruction.”
According to MAMA project documentation

Some details

MAMA give us answers on questions like: how many sites use CSS (80,4% by MAMA), how many errors on average page (47), how many symbols on average page (16,400), which country the most use XMLHttpRequest, an important component of AJAX? (Norway, 10.2%).

Or more sophisticated: how many sites adapted for mobile gadgets, how much Web2.0 spread, what version of HTTP protocol more popular and so on..

MAM is active project and so with the lapse of time we will get bigger range of data. That will give us possibility to understand Web tendencies and Web better.
So thanks Mama.

Related links links to get details:
Mama project description: [http://dev.opera.com/articles/view/mama/]
Mama key findings [http://dev.opera.com/articles/view/mama-key-findings/]

There is set of plug-ins that really simplify development process and glance will help you select something for your daily work.

golden list

name: firebug
functions: edit, debug, and monitor CSS, HTML, and JavaScript live
hints: page loading analysis, live working with CSS styles, JavaScript debugger
add-on page: [https://addons.mozilla.org/en-US/firefox/addon/1843]

name: user agent switcher
functions: switch the user agent of the browser
hints: cool but IE, and Firefox still interpret code differently and anyway for interpretation tests you need ‘ies4linux’ [http://www.tatanka.com.br/ies4linux/page/Main_Page]
add-on page: [https://addons.mozilla.org/en-US/firefox/addon/59]

name: dust-Me Selectors
functions:finds unused CSS selectors
add-on page: [https://addons.mozilla.org/ru/firefox/addon/5392]

name: firesizer
functions: resize of firefox the window to specific dimensions
hints: it helps to test site in required resolutions
add-on page: [https://addons.mozilla.org/en-US/firefox/addon/5792]

name: SQLite manager
functions: manage SQLite databases
hints: I think you know why it is better to use SQLite DB on workplaces
add-on page: [https://addons.mozilla.org/en-US/firefox/addon/5817]

name: add N edit cookies
functions: allows you add and edit session and saved cookies in live
add-on page: [https://addons.mozilla.org/en-US/firefox/addon/573]