here is the userContent.css file i added to the FF profile default folder C:\....\Application Data\M

here is the userContent.css file i added to the FF profile default folder C:\....\Application Data\Mozilla\Firefox\Profiles\z7hau5ip.default

@namespace url(http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul); html, address, blockquote, body, dd, div, dl, dt, fieldset, form, frame, frameset, h1, h2, h3, h4, h5, h6, noframes, ol, p, ul, center, dir, hr, menu, pre { display: block; unicode-bidi: embed } li { display: list-item } head { display: none } table { display: table } tr { display: table-row } thead { display: table-header-group } tbody { display: table-row-group } tfoot { display: table-footer-group } col { display: table-column } colgroup { display: table-column-group } td, th { display: table-cell } caption { display: table-caption } th { font-weight: normal; text-align: center } caption { text-align: center } body { margin: 8px } h1 {font-size:1.25em !important;} h2 {font-size:1.17em !important;} h3 {font-size:1.1em !important;} h4, p, blockquote, ul, fieldset, form, ol, dl, dir, menu { margin: 1.12em 0 } h5 { font-size: .83em; margin: 1.5em 0 } h6 { font-size: .75em; margin: 1.67em 0 } h1, h2, h3, h4, h5, h6, b, strong { font-weight: normal } blockquote { margin-left: 40px; margin-right: 40px } i, cite, em, var, address { font-style: italic } pre, tt, code, kbd, samp { font-family: monospace } pre { white-space: pre } button, textarea, input, select { display: inline-block } big { font-size: 1.17em } small, sub, sup { font-size: .83em } sub { vertical-align: sub } sup { vertical-align: super } table { border-spacing: 2px; } thead, tbody, tfoot { vertical-align: middle } td, th, tr { vertical-align: inherit } s, strike, del { text-decoration: line-through } hr { border: 1px inset } ol, ul, dir, menu, dd { margin-left: 40px } ol { list-style-type: decimal } ol ul, ul ol, ul ul, ol ol { margin-top: 0; margin-bottom: 0 } u, ins { text-decoration: underline } br:before { content: "\A"; white-space: pre-line } center { text-align: center } :link, :visited { text-decoration: underline } :focus { outline: thin dotted invert } }

AFAIK there has been no change on any webpage visited.

also installed firebug and extra tools, but that is hopelessly confusing.