Hi Anne, thanks for your comment. I so often hear “our users don’t need have accessibility needs”, but you describe an experience many of us have, indeed the majority of us us websites under less than perfect circumstances every day.
Although the style sheet switching on websites (often represented as an ‘aA’ icon) helps some people, designers have to attempt to offer what’s most useful, but given a multitude of viewing preferences risks missing a lot off people. I think we’re gradually overcoming the fallacy that most people enjoy reading tiny text and the move towards larger clearer typography will benefit everyone.
If you need bigger text some sites are trickier to read than others so the benefit of altering your (or your dad’s) viewing experience on a browser level is that you can tailor it to personal preference and apply it to all websites. Mozilla has an easy to follow guide for firefox support.mozilla.org/en-US/kb/change-fonts-and-colors-websites-use.
I bumped up the accessibility settings on my mums phone the other day, sadly the phone settings turned out to be a bit of a blunt instrument simply setting fonts to 120% original size – so sites with already generous font size ended up looking a bit silly, so not always a perfect solution.