[jandrese]

Is that a problem with the file input button, or with every other button on your website?

The file input button does seem to be a barely remembered feature by browser builders. It's weirdly specific, doesn't work the same way on phones, and probably only hangs around because there isn't a decent alternative.

[Jaruzel]

IIRC correctly, the File Input button was deliberately excluded from CSS styling, as it was felt that it would be abused to 'steal' data from clients, if the user wasn't aware it was file upload...