Can a website (HTML5,JavaScript) access a mobile device's (android/iPhone) contact list, SDCard files

There was an attempt at the W3C to create a browser API to access contacts from the browser. This is often mentioned as one of the new HTML5 APIs.

However the attempt never became a real specification and never got implemented by any browser vendors. Now it is officially discontinued:

http://www.w3.org/TR/contacts-api/

You can't access the mobile device file system through a website, it would be a major security problem. You might be able to steal all user files if you can access them through the browser. Hope this helps.

At this point in time there is no way to access the internal APIs from Android, iOS and Windows Phone via a simple website. This also precludes you from accessing aspects such as the contact list because these are all only accessible via API calls.

Solutions that allow you to code phone apps or web apps in JavaScript or HTML5 and still grant access to APIs do so by utilizing a wrapper with calls back to the native code. But you can't call native code from an external source such as a website.