gecko-dev/rdf/resources/sidebar.css

window { 
 display: block; 
} 

tree { 
 display: table; 
 background-color: #eeeeee; 
 border: none; 
 border-spacing: 0px; 
// border-collapse: collapse;
 width: 100%;
} 

treeitem { 
 display: table-row; 
} 

treehead { 
 display: table-header-group; 
} 

treebody { 
 display: table-row-group; 

} 

treecol {
 display: table-column;
 width: 200px;
}

treecell { 
 display: table-cell;
 font-family: Verdana, Sans-Serif;
 font-size: 8pt;
} 

treehead treeitem treecell { 
 background-color: #a0a0a0; 
 border: thin black solid; 
} 

treecell[selectedcell] {
 background-color: yellow;
 }
 
treecell[sortActive="true"] {
 background-color: #404040;
 }
 
treecol[sortActive="true"] {
  background-color: green;
}
  
treeitem[type="http://home.netscape.com/NC-rdf#Folder"] > treecell > titledbutton {
 list-style-image: url("resource:/res/rdf/bookmark-folder-closed.gif");
}

treeitem[type="http://home.netscape.com/NC-rdf#Folder"][open="true"] > treecell > titledbutton {
 list-style-image: url("resource:/res/rdf/bookmark-folder-open.gif");
}

treeitem[type="http://home.netscape.com/NC-rdf#Folder"][id="NC:PersonalToolbarFolder"] > treecell > titledbutton {
 list-style-image: url("resource:/res/rdf/personal-folder-closed.gif");
}

treeitem[type="http://home.netscape.com/NC-rdf#Folder"][id="NC:PersonalToolbarFolder"][open="true"] > treecell > titledbutton {
 list-style-image: url("resource:/res/rdf/personal-folder-open.gif");
}

treeitem[type="http://home.netscape.com/NC-rdf#Bookmark"] > treecell > titledbutton {
 list-style-image: url("resource:/res/rdf/bookmark-item.gif");
}

treeitem[type="http://home.netscape.com/NC-rdf#FileSystemObject"][container="true"][open="true"] > treecell > titledbutton {
 list-style-image: url("resource:/res/rdf/folder-open.gif");
}

treeitem[type="http://home.netscape.com/NC-rdf#FileSystemObject"][container="true"] > treecell > titledbutton {
 list-style-image: url("resource:/res/rdf/folder-closed.gif");
}

treeitem[type="http://home.netscape.com/NC-rdf#FileSystemObject"] > treecell > titledbutton {
 list-style-image: url("resource:/res/rdf/article.gif");
}