Mathjax ( https://www.mathjax.org/ ) encodes the equations without images, so you can rescale your browser page and the equations will always be readable.  As a specific example, take a look at a page that uses mathjax, such as:

http://peeterjoot.com/2016/01/05/energy-momentum-tensor-for-a-scalar-field/

No amount of control-plus-minus in your browser will make the equations fuzzy.  Compare that to a page that uses latex generated images, like:

https://steemit.com/mathematics/@dkmathstats/right-angle-triangles-and-the-soh-cah-toa-acronym

On this page, control+ a few times makes the c^2 = a^2 + b^2 really fuzzy.  

Many mathjax engines, such as the one that is used on stackexchange, physicsforums and the wordpress plugin mentioned) have latex equation parsers, so you can write your equations just as you would normally when doing latex -> pdf, but they can be rendered nicely in html.