I would like to zoom-out all the page to the scale 0.5, so I add the META tag as follow: <META HTTP-Equiv="zoom" Content="page:0.5">.
But there is nothing on display, if I set the parameter greater than 1.0, it is OK. But I want to Zoom-out page, not Zoom-in.
Please kindly give me some advice.
There's a known bug with version 2.0 / 2.1 where you must specify your zoom factor as an integer, ie you can't provide a fractional zoom. The syntax of your tag is correct.