[BNM] Controlling / Restricting Max & Min Text Sizes

[Chris Adams]

Generally I use ems to control text within a page with a body text-size 
starting at 0.7em. As is of great importance I want to give my users the 
ability to resize at will, keeping my sites as accessible as possible.
Problem that I consistently find is (in particular) ie when you change 
the browser text size prefs to 'Larger' or heaven forbid 'Largest' the 
relative size of the text shoots through the roof. Likewise reducing the 
size of the text to 'Smallest' turns it into incy wincey ant size 
illegible text.
Is there an obvious, accessible and validatable way of controlling this 
text size or are we totally at the whim of crazy bugger text resizing?
In anticipation of someone telling me how simple it is to make this 
so... thanks ;]
Chris