How to Apply global font to whole HTML document

Question

You should be able to utilize the asterisk and !important elements within CSS.

html *
{
   font-size: 1em !important;
   color: #000 !important;
   font-family: Arial !important;
}

The asterisk matches everything (you could probably get away without the html too).

The !important ensures that nothing can override what you've set in this style (unless it is also important). (this is to help with your requirement that it should "ignore inner formatting of text" - which I took to mean that other styles could not overwrite these)

The rest of the style within the braces is just like any other styling and you can do whatever you'd like to in there. I chose to change the font size, color and family as an example.

Best practice I think is to set the font to the body:

body {
    font: normal 10px Verdana, Arial, sans-serif;
}

and if you decide to change it for some element it could be easily overwrited:

h2, h3 {
    font-size: 14px;
}

Set it in the body selector of your css. E.g.

body {
    font: 16px Arial, sans-serif;
}

Use the following css:

* {
    font: Verdana, Arial, 'sans-serif' !important;/* <-- fonts */
}

The *-selector means any/all elements, but will obviously be on the bottom of the food chain when it comes to overriding more specific selectors.

Note that the !important-flag will render the font-style for * to be absolute, even if other selectors have been used to set the text (for example, the body or maybe a p).