Hi, will this work instead  ?, is more than asked for :

• https://addons.mozilla.org/en-US/firefox/addon/theme-font-size-changer

Thanks, but (I think) not: too complicated to me and a large number of unnecessary features (for my purpose), too!

userChrome.css is custom made and not something that FF forum can really help with in programming. You have to check with the site that you used to get the userChrome.css changes.

Hi Patrick, the @-moz--document rule is causing the problem. It may be possible to figure out a new URL but it's probably easier to drop it because the selectors are specific enough.

/* Default font size and face for Sidebar */
.sidebar-placesTree {
  font-size: 11px;
  font-family: Verdana;
}
/* Folder title color and weight for Sidebar */
.sidebar-placesTree treechildren::-moz-tree-cell-text(title, container) {
  color: blue !important;
  -moz-border-radius: 2em !important;
  font-weight: bold;
}
/* Remove Delete from context menu for Bookmarks Sidebar */
#bookmarksPanel #placesContext_delete,
#bookmarksPanel #placesContext_deleteSeparator {
  display:none !important;
}

Thank you very much jscher2000 for your kind reply; I tried but th problem is still there.

Since I know very little about these things, maybe I'm doing something wrong, so I write down my current Userchrome (I didn't write it: it is a collection of information I've found); I hoper this help to find where the problem is: .....................

#bookmarksPanel .sidebar-placesTreechildren::-moz-tree-row(selected) {
background: #FF00FF !important;
} 

#bookmarksPanel treechildren::-moz-tree-cell-text(selected) {
  color: #fffff0 !important;
  font-weight: bold !important; }

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

/* Modifiche al font usato nella barra laterale dei segnalibri */

@-moz-document url("chrome://browser/content/bookmarks/bookmarksPanel.xul")
{
.sidebar-placesTree {
font-size: 11px;
font-family: Verdana;
}
treechildren::-moz-tree-cell-text(title, container) {
color: blue !important;
-moz-border-radius: 2em !important;
font-weight: bold;
}
}

#bookmarksPanel #placesContext_delete {
display:none !important;
}

/* Nasconde la floating status bar (da Firefox 25) */

statuspanel { 
   display: none !important; }

/* Diminuisce la larghezza minima della barra laterale dei segnalibri */

#sidebar-box {
   min-width: 5px !important; }

tab[class="tabbrowser-tab"] {
	font-family: Verdana !important;
}

/*Remove bookmark toolbar tooltips*/
#bhTooltip { display: none !important; }


/* Cambia il colore del separatore */
#bookmarks-view .sidebar-placesTreechildren::-moz-tree-separator {
 -moz-appearance: none !important;
  border-color: #C0B0B0 !important; }

/* Colored folders for bookmark sidebar, toolbar, menu button */
  /* Standard folder */
#bookmarks-view treechildren::-moz-tree-image(container),
#PlacesToolbarItems toolbarbutton[container="true"] .toolbarbutton-icon,
#PlacesToolbarItems menu[container="true"] .menu-iconic-left,
#BMB_bookmarksPopup menu[container="true"] .menu-iconic-icon {
  fill: #ff8000 !important; /* slightly muted gold */
}
  /* Live Bookmark (RSS Feed) */
#bookmarks-view treechildren::-moz-tree-image(container, livemark),
#PlacesToolbarItems toolbarbutton[container="true"][livemark="true"] .toolbarbutton-icon,
#PlacesToolbarItems menu[container="true"][livemark="true"] .menu-iconic-left,
#BMB_bookmarksPopup menu[container="true"][livemark="true"] .menu-iconic-icon {
  fill: orange !important;
}
  /* Smart bookmark folder */
#bookmarks-view treechildren::-moz-tree-image(container, query),
#PlacesToolbarItems toolbarbutton[container="true"][query="true"] .toolbarbutton-icon,
#PlacesToolbarItems menu[container="true"][query="true"] .menu-iconic-left,
#BMB_bookmarksPopup menu[container="true"][query="true"] .menu-iconic-icon {
  fill: #69c !important; /* similar to blue smart folder color */
}
  /* These "containers" are SVG in the sidebar, not yet on the menu */
#bookmarks-view treechildren::-moz-tree-image(container, OrganizerQuery_BookmarksMenu) {
  fill: olive !important;
}
#bookmarks-view treechildren::-moz-tree-image(container, OrganizerQuery_BookmarksToolbar) {
  fill: olive !important;
}
#bookmarks-view treechildren::-moz-tree-image(container, OrganizerQuery_UnfiledBookmarks) {
  fill: olive !important;
}

#statuspanel:not([type="overLink"]) {
  opacity: 0 !important;
}

.....................................................

Please see the attached screenshots regarding the edits.

Jscher2000,

I have only one word: AMAZING!!!!

In my country we say "un'immagine vale più di mille parole" (something like "one image is much better than 1000 words"  ;-) )

I followed your instruction and... IT WORKS PERFECTLY!

I do not know how to thank you, you have just solved one of two most annoying problem of mine with Firefox (I have just posted the other one.... ;-))

Thanks again... a BIG GRAZIE from Italy!!!