How to determine font size visible to user in IE?

I wonder what would be the best way to catch the font size visible to user in IE. I cannot depend on size related html tags, because they are not inside the html page s开发者_C百科ource code. Somehow I need a way to capture the font visually on browser and determine the font size.

What would you suggest for this?

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I think this article of AListApart will help you, or at least give you some ideas:

http://www.alistapart.com/articles/fontresizing