Remove Firefox new Megabar design, generated with https://www.userchrome.org/megabar-styling-firefox-address-bar.html#mbarstyler

userChrome.css

/*** Megabar Styler General - version 2020-04-19 ***/



  /*** General Preferences ***/

  :root {

    /* Number of pixels of enlargement when URL bar is focused */

    --mbarstyler-popout-pixels: 0px; /* [0px - 7px] */



    /* Top Bar Display or Not */

    --mbarstyler-top-bar-display: block; /* [block,none] */



    /* Font sizes (default: 13.8px for title, 10.2px for URL) */

    --mbarstyler-title-font-size: 15px; /* [13px - 18px] */

    --mbarstyler-url-font-size: 13px; /* [12px - 16px] */



    /* Rows to show without scrolling */

    --mbarstyler-max-rows-without-scrolling: 10;



    /* Bottom border for each result row */

    --mbarstyler-bottom-border-width: 0px; /* [0px or 1px] */

    

    /* Match display style */

    --mbarstyler-match-weight: 700; /* [400,700] */

    --mbarstyler-match-background-opacity: 0.0; /* [0.0,0.05,0.1] */

  }



  /*** URL bar enlargement or lack thereof ***/



  /* Compute new position, width, and padding */

  #urlbar[breakout][breakout-extend] {

    top: calc(5px - var(--mbarstyler-popout-pixels)) !important;

    left: calc(0px - var(--mbarstyler-popout-pixels)) !important;

    width: calc(100% + (2 * var(--mbarstyler-popout-pixels))) !important;

    padding: var(--mbarstyler-popout-pixels) !important;

  }

  [uidensity="compact"] #urlbar[breakout][breakout-extend] {

    top: calc(3px - var(--mbarstyler-popout-pixels)) !important;

  }

  [uidensity="touch"] #urlbar[breakout][breakout-extend] {

    top: calc(4px - var(--mbarstyler-popout-pixels)) !important;

  }



  /* Prevent shift of URL bar contents */

  #urlbar[breakout][breakout-extend] > #urlbar-input-container {

    height: var(--urlbar-height) !important;

    padding: 0 !important;

  }



  /* Do not animate */

  #urlbar[breakout][breakout-extend] > #urlbar-background {

    animation: none !important;;

  }



  /* Remove shadows */

  #urlbar[breakout][breakout-extend] > #urlbar-background {

    box-shadow: none !important;

  }



  /*** Top "Blue Bar" Display ***/



  .urlbarView-row:first-of-type {

    display: var(--mbarstyler-top-bar-display) !important;

  }



  /*** Font Sizes and Scrolling ***/



  /* Title font-size */

  .urlbarView-row .urlbarView-title {

    font-size: var(--mbarstyler-title-font-size) !important;

  }



  /* URL / action font-size */

  .urlbarView-row .urlbarView-secondary,

  .urlbarView-row .urlbarView-url,

  .urlbarView-row .urlbarView-action {

    font-size: var(--mbarstyler-url-font-size) !important;

  }



  /* Set max-height for items visible without scrolling */

  #urlbarView-results, #urlbar-results {

    height: unset !important;

    max-height: calc(2.5 * (var(--mbarstyler-title-font-size) + var(--mbarstyler-bottom-border-width)) * var(--mbarstyler-max-rows-without-scrolling)) !important;

  }

  #urlbar-results {

    overflow-y: auto !important; 

  }



  /* Clean up extra spacing at the top and bottom */  

  #urlbar-results {

    padding-top: 0 !important;

    padding-bottom: 0 !important;

  }



  /* Subtle border between results */

  .urlbarView-row:not(:last-of-type) {

    border-bottom: var(--mbarstyler-bottom-border-width) solid rgba(0, 0, 0, 0.1) !important;

  }



  /* Match Styling Like Fx43-47 */

  [lwt-popup-darktext] .urlbarView-row:not([selected]) .urlbarView-title strong,

  [lwt-popup-darktext] .urlbarView-row:not([selected]) .urlbarView-url strong {

    font-weight: var(--mbarstyler-match-weight) !important;

    box-shadow: inset 0 0 1px 1px rgba(0, 0, 0, calc(var(--mbarstyler-match-background-opacity) * 2));

    background-color: rgba(0, 0, 0, var(--mbarstyler-match-background-opacity));

    border-radius: 2px;

  }

  [lwt-popup-brighttext] .urlbarView-row:not([selected]) .urlbarView-title strong,

  [lwt-popup-brighttext] .urlbarView-row:not([selected]) .urlbarView-url strong {

    font-weight: var(--mbarstyler-match-weight) !important;

    box-shadow: inset 0 0 1px 1px rgba(255, 255, 255, calc(var(--mbarstyler-match-background-opacity) * 2));

    background-color: rgba(255, 255, 255, var(--mbarstyler-match-background-opacity));

    border-radius: 2px;

  }



/*** End of: Megabar Styler General ***/