~/Library/Application Support/Firefox/Profiles/xxxxxxx.default/chrome/userChrome.css

userChrome.css for FF4 OSX

/* Tab Arrangement */
.tab-close-button { -moz-box-ordinal-group: 1 !important;}
.tab-text { -moz-box-ordinal-group: 2 !important;}
.tab-throbber { -moz-box-ordinal-group: 3 !important;}
.tab-icon-image { -moz-box-ordinal-group: 4;}

.tabbrowser-tab[pinned] .tab-icon-image {
visibility: visible !important;
}

/* Hide Tab Close Buttons */
.tab-close-button {
visibility: hidden !important;
}
tab:hover .tab-close-button {
visibility: visible !important;
}

/* Hide Toolbar Facicons */
.bookmark-item > .toolbarbutton-icon {
display: none !important;
}

/* Personal Toolbar smaller */
#PersonalToolbar {
padding-top: 1px !important;
padding-bottom: 2px !important;
}

/* Personal Bookmarks smaller */
#personal-bookmarks menu,
#personal-bookmarks menuitem {
max-width: 460px !important;
font-size: 10pt !important;
}

/* Awesome Bar stuff */
#urlbar .autocomplete-history-dropmarker {
display: none !important;
}
.autocomplete-richlistitem:not(:first-child) {
border-top: 1px solid #e6e6e6 !important;
}
.ac-url-text {
color: #959595 !important;
}
.ac-url-text[selected="true"] {
color: white !important;
}

/* Searchbar stuff */
.searchbar-engine-image {
visibility: hidden !important;
width: 9px !important;
}
.searchbar-textbox > .autocomplete-textbox-container {
background-image: url("chrome://browser/skin/Search.png") !important;
background-repeat: no-repeat !important;
background-position: 4px 4px !important;
}
.search-go-button {
display: none !important;
}

/* Sidebar stuff */
sidebarheader {
-moz-box-direction: reverse !important;
text-align: center !important;
padding-right: 26px !important;
padding-bottom: 0px !important;
}
treechildren::-moz-tree-separator {
border-top: 1px dashed #6f8b9f !important;
}
#sidebar-splitter:-moz-window-inactive {
-moz-border-end: 1px solid #8B8B8B !important;
}