I believe the you want the CSS id selector "#writeup" for the initial post, and the CSS class selector ".reply-body" or ".notes" for replies. (".reply-body" seems to be more specific, so it is probably the one you want there.)

For sizing, you can do something like 125%, 1.5em or 1.75rem (1.25x the font size of the parent element, 1.5x the font size of the parent element or 1.75x the font size of the root HTML element (<html>), respectively), or specify a size such as "medium", "large", "x-large", or "xx-large" (there's also "xx-small", "x-small", and "small").

The following example should increase the size of an initial writeup to 1.5x default, and responses to 1.25x default: 

/* Guesswork from inspecting a random page. */
/* writeup - class for original posts (?) */
#writeup {
    font-size: 1.5em;
    /* or 1.5rem, or 150% */
}
/* reply-body - class for responses (?) */
#reply-body {
    font-size: 1.25em;
    /* or 1.25rem, or 125% */
}

[download]

Hope that helps.

In reply to Re: css for bigger font by atcroft
in thread css for bigger font by slowsort

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