I believe it was originally introduced for sight impaired users, not mobile apps.

>Yes, there are ways to do it. Initially, it was introduced for mobile apps because this creates a lot of problem if the user increases the size of a Web page. Then, some browsers started to support it for the desktop. I haven't made any test for HTML 5 yet. This is yet to be done.
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>However, this is an interesting link which explains how to set it back to 100%:
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>http://www.smartsheet.com/help/browser-zoom