If the user ever has to push a "retry" button, the networking levels are very badly designed. Just because some crappy web sites work that way does not mean it's OK.
The user shouldn't _have_ to. However, a 'refresh state' (and validate state, more gracefully than a full kill and reload) button can be both helpful and psychologically reassuring.
It can also be very helpful for out of band issues, like ISP hiccups, random hardware failures, bitflips, etc.
If the user ever has to push a "retry" button, the networking levels are very badly designed. Just because some crappy web sites work that way does not mean it's OK.