How can I force pinch-to-zoom on some websites? As someone with vision issues I typically need to zoom on every single page I load on my iPhone.  

The "three finger tap" to zoom kinda sucks, so pinch to zoom works great. However since upgrading to iPhone 4S I've noticed a lot of sites don't allow it.

I know there's a meta tag you can use to disable that feature, but is there an override that you can set to be able to zoom on every page?  I can't zoom in on google results, so I can't really see them. NFL.com doesn't allow pinch to zoom either.
Ugh, this is so annoying -- it is the height of designer/developer arrogance (in my opinion -- and I'm a developer myself). The other answer's code did not work for me, but after much experimenting I got this to work (iPad 3/iOS 5):

javascript:document.querySelector('meta[name=viewport]').setAttribute('content','width=device-width,initial-scale=1.0,maximum-scale=10.0,user-scalable=1');


Use the same method as the other answer says to add it (create a bookmark for any page, then edit the bookmark and replace its URL with the above code).