diff --git a/locales/en-US/chrome/chatzilla.properties b/locales/en-US/chrome/chatzilla.properties
--- a/locales/en-US/chrome/chatzilla.properties
+++ b/locales/en-US/chrome/chatzilla.properties
@@ -1297,17 +1297,17 @@ msg.you.quit     = YOU (%S) have left %S
 msg.someone.quit = "%S has left %S (%S)
 
 msg.unknown.ctcp = Unknown CTCP %S (%S) from %S"
 
 msg.fonts.family.fmt   = Font family is ``%S''
 msg.fonts.family.pick  = Enter the font family you wish to use:
 msg.fonts.size.fmt     = Font size is %Spt
 msg.fonts.size.default = Font size is default
-msg.fonts.size.pick    = Enter the font size you wish to use:
+msg.fonts.size.pick    = Enter the font size you wish to use. Note: Non-numeric inputs will result in the default size.
 
 msg.supports.chanTypes = Supported channel types: %S"
 msg.supports.chanModesA = Supported channel modes (A: lists): %S"
 msg.supports.chanModesB = Supported channel modes (B: param): %S"
 msg.supports.chanModesC = Supported channel modes (C: on-param): %S"
 msg.supports.chanModesD = Supported channel modes (D: boolean): %S"
 msg.supports.userMode = "%S (%S)
 msg.supports.userModes = Supported channel user modes: %S"
@@ -1531,17 +1531,17 @@ pref.desc.label                 = Descri
 pref.desc.help                  = Sets the "description" (aka "real name") field shown in your /whois information. It is commonly used to include one's real name, but you are not required to enter anything.
 pref.deleteOnPart.label         = Delete channel views on part
 pref.deleteOnPart.help          = Causes /leave and /part to also close the channel view.
 pref.displayHeader.label        = Show header
 pref.displayHeader.help         = Display the chat header on this view. This contains information like the URL of the current view, and the topic and modes for a channel view.
 pref.font.family.label          = Font Family
 pref.font.family.help           = Selects the font in which ChatZilla will display messages. The value "default" will use your global font family; "serif", "sans-serif" and "monospace" will use your global font settings; other values will be treated as font names.
 pref.font.size.label            = Font Size (pt)
-pref.font.size.help             = Selects the font size you want ChatZilla to display messages with. The value 0 will use your global font size, and other values will be interpreted as the size in points (pt).
+pref.font.size.help             = Selects the integer font size you want ChatZilla to display messages with. The value 0 will use your global font size, and other integer values will be interpreted as the size in points (pt).
 pref.guessCommands.label        = Guess unknown commands
 pref.guessCommands.help         = If you enter a command (starts with "/") that ChatZilla doesn't understand, then it can try "guessing" by sending the command to the server. You can turn this off if you don't want ChatZilla to try this.
 pref.hasPrefs.label             = Object has prefs
 pref.hasPrefs.help              = Indicates the object has preferences saved. Never shown in preferences window. :)
 pref.identd.enabled.label       = Enable Identification Server during connection process
 pref.identd.enabled.help        = Allows ChatZilla to connect to servers that require an ident response.
 pref.initialURLs.label          = Locations
 pref.initialURLs.help           = A list of locations (irc: and ircs: URLs) to which ChatZilla should connect when starting. These will not be processed if ChatZilla was started by clicking on a hyperlink.
diff --git a/xul/content/commands.js b/xul/content/commands.js
--- a/xul/content/commands.js
+++ b/xul/content/commands.js
@@ -3974,16 +3974,19 @@ function cmdFont(e)
                     val = pVal - 2;
                     break;
 
                 case "bigger":
                     val = pVal + 2;
                     break;
 
                 default:
+                    if (isNaN(val))
+                        val = 0;
+                    else
                     val = Number(val);
             }
             // Save the new value.
             view.prefs[pref] = val;
         }
 
         // Show the user what the pref is set to.
         if (view.prefs[pref] == 0)
diff --git a/xul/content/config.js b/xul/content/config.js
--- a/xul/content/config.js
+++ b/xul/content/config.js
@@ -570,16 +570,18 @@ function pdata_loadXUL()
             label = document.createElement("label");
             label.setAttribute("value", this.label);
             label.width = 100;
             label.flex = 1;
             this.box.appendChild(label);
             
             this.edit = document.createElement("textbox");
             this.edit.setAttribute("size", "5");
+            this.edit.setAttribute("type", "number");
+            this.edit.setAttribute("min", "-1");
             
             editCont = document.createElement("hbox");
             editCont.flex = 1000;
             editCont.appendChild(this.edit);
             this.box.appendChild(editCont);
             break;
             
         case "boolean":