Although some browsers might allow you to disable CSS, this can also cause problems with some files. One thing is that some implementations of form fields will not work at all with CSS disabled. One alternative would be a mode to use ARIA for styling instead of CSS. If the web page uses ARIA to denote the custom form fields and other stuff, then this might work; however, I do not know of any implementation that is capable of using ARIA for such a purpose (usually they use ARIA only for people with disabilities, but it could be useful for anyone, I think).