Just recently Google Reader enabled a cool features and which will help you to increase or decrease the font size on reading section. Just press + to enlarge the font size and - to decrease the fonts size. Just content section’s font will increase, not the full web pages.
If you’re mozilla/netscape user, you can increase the full web pages size to press ctrl and + and as well as ‘-’ for font size decreasing or back to default setup you can use ctrl+0. But it has some problem when in everywhere the the font size increasing or decreasing and has no specification. So, Google Reader created alternative option and hope this will create more concentration on your reading 
Increase font size in google reader [via googlesystem]
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