Firefox UserChrome.css

@namespace url(http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul);

* { 
    font-size: 8pt !important;
    font-family: "Verdana" !important; 
} 

.newtab-cell {
    margin-bottom: 0px !important;
    margin-top: 0 !important;
}
.newtab-site, .newtab-thumbnail, .newtab-cell {
    border-radius: 0 !important;
}

#navigator-toolbox #PersonalToolbar:not(:-moz-lwtheme) {
    background: transparent !important;
    background-color: -moz-dialog !important;
    opacity: 1.0 !important;
}
#navigator-toolbox #PersonalToolbar toolbarbutton {
    font-size:11px !important;
    font-family: "Tahoma" !important;
    text-shadow: 0 0 1px white !important;
}


#identity-box {
    background: transparent !important;
}


/*Tabs*/

.tab-text {
  font-size: 8pt !important;
}

#TabsToolbar {
    /*background: transparent !important;*/
    margin-bottom: 0 !important;
}

#TabsToolbar .arrowscrollbox-scrollbox {
    padding: 0 !important;
}

#TabsToolbar .tabbrowser-tabs{
    min-height: 26px !important;
    margin-top: 1px !important;
}

#TabsToolbar .tabbrowser-tab{
    background-clip: padding-box !important;
    margin-left: -1px;
    min-width:16px !important;
    opacity: 1.0 !important;
    border: 1px solid transparent !important;
    border-bottom: none !important;
    background-color: rgba(255,255,255,0.0) !important;
    text-shadow: 0 0 1px rgba(100,100,100,0.6) !important;
}

#TabsToolbar .tabbrowser-tab[first-tab] {
    margin-left: 0 !important;
}

#TabsToolbar .tabs-newtab-button{
    -moz-border-top-colors: none !important;
    -moz-border-left-colors: none !important;
    -moz-border-right-colors: none !important;
    -moz-border-bottom-colors: none !important;
    border-style: solid !important;
    border-color: transparent !important;
    border-width: 1px 1px 0 1px !important;
    text-shadow: 0 0 4px rgba(255,255,255,.75) !important;
    background: transparent !important;
    background-clip: padding-box !important;
    transition: all .1s;
    margin-left: 0 !important;
}


/*
#TabsToolbar .tabbrowser-tab[first-tab][last-tab],#TabsToolbar .tabbrowser-tab[last-visible-tab]{
    border-right-width: 1px !important;
}

#TabsToolbar .tabbrowser-tab[afterselected]{
   border-left-color: rgba(0,0,0,.25) !important;
}
*/

#TabsToolbar .tabbrowser-tab[selected]{
    background-clip: padding-box !important;
    opacity: 1.0 !important;
    border: 1px solid threedshadow !important;
    border-bottom: none !important;
}

#TabsToolbar .tabbrowser-tab[selected]:not(:-moz-lwtheme) {
    background-color: rgba(246,246,246, 1.0) !important;
    background-color: -moz-dialog !important;
    color: black !important;
    opacity: 1.0 !important;
}

#TabsToolbar .tabbrowser-tab[selected]:-moz-lwtheme {
    background: linear-gradient(0deg, rgba(240,240,240, 0.0), rgba(240,240,240,0.9)) !important;
}

#TabsToolbar .tabs-newtab-button:hover, #TabsToolbar .tabbrowser-tab:hover:not([selected]){
    border-color: rgba(0,0,0,.2) !important;
    background-color: rgba(255,255,255,.55) !important;
}

#TabsToolbar .tab-background{
    margin: 0 !important;
    background: transparent !important;
}

#TabsToolbar .tab-background-start, #TabsToolbar .tab-background-end{
    display: none !important;
}

#TabsToolbar .tab-background-middle{
    margin: -4px -2px !important;
    background: transparent !important;
}

#TabsToolbar .tabbrowser-tab:after, #TabsToolbar .tabbrowser-tab:before{
    display: none !important;
}

#TabsToolbar .tabs-newtab-button{
    border-width: 1px 1px 0 1px !important;
    margin: 0 0 0 1px !important;
    width: auto !important;
    padding: 0 5px !important;
}

#nav-bar {
    height: 38px;
    box-shadow: none !important;
}

#nav-bar:not(:-moz-lwtheme) {
    opacity: 1.0 !important;
    background: transparent !important;
    /*background: linear-gradient(0deg, #dfe8ff 30%, #BFDBF7) !important;*/
    /* -------------------------------^^^^^^^              bottom gradient color, should match the bookmark toolbar color */
    /* --------------------------------------------^^^^^^^ top gradient color, should match the active tab color */  
    background-color: -moz-dialog !important;
}
/* forward button always visible */

window:not([chromehidden~="toolbar"]) #urlbar-container > #forward-button {
    border-right: 1px solid #AEB7BF !important;
}

window:not([chromehidden~="toolbar"]) #urlbar-container > #forward-button[occluded-by-urlbar] {
    visibility: visible;
}

window:not([chromehidden~="toolbar"]) #urlbar-container:not(:hover) > #forward-button[disabled] {
    opacity: 1;
}

window:not([chromehidden~="toolbar"]) #urlbar-container[forwarddisabled] > #urlbar-wrapper {
    clip-path: none;
}

window:not([chromehidden~="toolbar"]) #urlbar-container[forwarddisabled][switchingtabs] + #urlbar-container > #urlbar,
window:not([chromehidden~="toolbar"]) #urlbar-container[forwarddisabled]:not(:hover) > #urlbar-wrapper > #urlbar {
    margin-left: 0;
}

window:not([chromehidden~="toolbar"]) #urlbar-container[forwarddisabled][switchingtabs] + #urlbar-container > #urlbar > #notification-popup-box[hidden] + #identity-box:-moz-locale-dir(ltr),
window:not([chromehidden~="toolbar"]) #urlbar-container[forwarddisabled]:not(:hover) > #urlbar-wrapper > #urlbar > #notification-popup-box[hidden] + #identity-box:-moz-locale-dir(ltr) {
    padding-left: 2px;
}