gecko-dev/browser/components/console/content/console.css

.console-box {
  -moz-binding: url("chrome://browser/content/console/consoleBindings.xml#console-box");
  overflow: auto;
}

.console-rows {
  -moz-user-focus: normal;
}

.console-row[type="error"],
.console-row[type="warning"] {
  -moz-binding: url("chrome://browser/content/console/consoleBindings.xml#error");
}

.console-row[type="message"] {
  -moz-binding: url("chrome://browser/content/console/consoleBindings.xml#message");
}

.console-error-msg {
  white-space: normal;
}
    
.console-msg-text {
  white-space: pre;
}  

.console-error-source {
  -moz-binding: url("chrome://browser/content/console/consoleBindings.xml#console-error-source");
}
  
/* :::::::::: hiding and showing of rows for each mode :::::::::: */

.console-box[mode="Warnings"] > .console-box-internal > .console-rows 
    > .console-row[type="error"],
.console-box[mode="Messages"] > .console-box-internal > .console-rows 
    > .console-row[type="error"]
{
  display: none;
}  
  
.console-box[mode="Errors"] > .console-box-internal > .console-rows 
    > .console-row[type="warning"],
.console-box[mode="Messages"] > .console-box-internal > .console-rows 
    > .console-row[type="warning"]
{
  display: none;
}  
  
.console-box[mode="Errors"] > .console-box-internal > .console-rows 
    > .console-row[type="message"],
.console-box[mode="Warnings"] > .console-box-internal > .console-rows 
    > .console-row[type="message"]
{
  display: none;
}