How can you find out if a specific HTML 5 feature is implemented in a specific browser version?

Question

I imagine there must be out there a website that collects information about HTML 5 feature and what browsers version started to support them.

This might be a good way to decide based on your website profile, if you can apply that HTML 5 feature without a fallback for your visitors.

Do you know such a site/resource ?

For example I want to know what browsers support the multiple upload feature for inputs and what browser version was the first.

Update

I'm not pleased with the sites suggested so I'm opening a bounty.

Suggestions so far:

Html5Test,

Caniuse,

modernizr.com,

QuirksMode

Update 2

Some people don't understand the question. I need to implement the multiple upload feature. I know from analytics what browser are they using ( I know this is not 100% correct ).

I'm willing to sacrifice some of the visitors by not offering some advance features but I need to understand how big is this procent. I'm NOT trying to DETECT in anyway the browser. It's a similar approach with other sites that dropped IE 6 support.

So please don't talk about bad practice.

Answer 1

Try to look at Html5Test or caniuse.

Answer 2

If it's server side, you can analyze user agent to find out if client's version supports HTML5. Wikipedia is your friend. If it's client side, there's Modernizr library.