Most mobile browsers implement some sort of text inflation algorithm but if your site is set up to properly size the text you can disable this behavior. The text-size-adjust property is non-standard so, at the moment, it can only be used with vendor specific prefixes.
There are a few different values that can be passed to the text-size-adjust property for differing effects.
none— disables the default browser text inflation
auto— is intended as an override for the none value, it lets the browser know to go ahead and apply its text inflation
percentage— this value is a percentage of the browser’s default text inflation, when set it will increase or decrease the default browser font size by the percentage specified
The text-size-adjust property is non-standard, but luckily the most popular mobile browsers do support it using vendor specific prefixes.