The default location for mon.cgi is your /cgi-bin path on your web server.

By default the mon.cgi.cf file location should be in /etc/mon where the base config directory is set.

Here is the default config file that is included with mon.cgi:

#
# The mon.cgi config file.
# Format:
#        key = value
#
# Blank lines and lines that begin with '#' are ignored.
#
# Both key names and values are case sensitive.
#
# This file comes with the mon.cgi distribution and contains all of the
# valid key/value pairs that mon.cgi will accept.
#
# The latest version of mon.cgi is always available at:
#     http://www.ryanclark.org/files/mon/
#
# If there are errors in your config file, mon.cgi will stop parsing it,
# and will print messages to STDERR, which should end up in your web
# server's error log.
#
# $Id: index.html,v 1.1 2004/12/31 01:35:36 ryan Exp $
#

# Your organization (what you want printed on the top of each page)
organization = Mon.cgi CSS Support

# Contact email for mon administrator at your site
monadmin = rlclark@gmail.com

#Company or mon logo (URL path)
logo = your_logo.png

# URL to go to when you click on the logo image
logo_link = http://www.kernel.org/pub/software/admin/mon/html/

# Seconds between page reload
reload_time = 180

# Where to run mon (host,port)
monhost = localhost
monport = 2583

# Set this to anything other than 'Y' or 'yes' to turn off authentication
# (HINT: authentication is a *good* thing)
must_login = yes

# Application secret. Set this to something long and unguessable.
app_secret = LKAHETOI#KJHJKSHDOWOIUW^*((985i2hkljlkjfdhglkdhfgdlkfjghldksfjhg98 34tklh  qrthq3 i3lu4
KLHKLJHKLJH ncxmvn owow y YnneO87210502673kn6l3

# Default username and password (only used if must_login is set)
default_username = readonly
default_password = public

# Idle time, in seconds, until login cookie is invalidated. Note that if
# ( login_expire_time < reload_time ) you will not be able to "idle".
login_expire_time = 900

# Whether or not to untaint HTML in ack msgs using HTML::Entities (recommended)
untaint_ack_msgs = yes

# The name of the cookie set by mon.cgi and its path
cookie_name = mon-cookie
cookie_path = /

# CSS Sheet (relative to your webroot)
css_style = /moncgi.css

# Maximum number of downtime events to show, per page
dtlog_max_failures_per_page = 100

# Watch keywords will show only the specified hostgroups by default.
# Matching is by regexp.
# e.g., show the watch whose name is www
#watch = www
# e.g., show any watches whose names start with gw-
#watch = gw-.*

# Set show_watch_strict to 'yes' if you want to be sure that users only
# information about the hostgroups that they are authorized to
# view. If show_watch_strict is set to 1, as far as your GUI users
# will know, there is nothing else running on the mon instance
# except for their hostgroups, *even if those users know the names
# of other hostgroups on your mon server*.
#
# Set to show_watch_strict to 'no' to show only the defined watch
# groups by default, but allow users to see information about
# others as well.
show_watch_strict = no

The default location for the moncgi.css file is in your web root on your webserver.

Here are the following tags/classes that have CSS sheet applied to them:

Here is the default CSS sheet for mon.cgi to use:

/* ----------------------------------------------
Default CSS Theme for Mon.cgi - http://www.kernel.org/pub/software/admin/mon/html/
By Ryan Clark - http://www.ryanclark.org
v1.0 - August 2004 - Validates as CSS3
$Header: /home/cvs/cos/rep/sites/org/ryanclark/www/files/mon.cgi/docs/index.html,v 1.1 2004/12/31 01:35:36 ryan Exp $
---------------------------------------------- */
/* ----------------------------------------------
General page layout
---------------------------------------------- */
body {
	margin : 0;
	padding : 0;
	background : #eee;
	color : #111;
	font-size: 80%;
	font-family: 'Lucida Grande', Verdana, Geneva, Lucida, Helvetica, Arial, sans-serif;
}

table {
	color: #404040;
	background-color: #fafafa;
	border: 1px #999999 solid;
	border-collapse: collapse;
	border-spacing: 0px;
	margin-top: 0px;
}

table#log {
	font-size: 80%;
}

.hosts {
        font-family: 'Lucida Grande', Verdana, Geneva, Lucida, Helvetica, Arial, sans-serif;
        font-weight: bold;
        margin: 10px 0 10px 0;
        border-bottom : 1px #eee;
}

.time {
        font: 85%/125% 'Lucida Grande', Verdana, Geneva, Lucida, Helvetica, Arial, sans-serif;
        letter-spacing: -1px;
}


.navigation {
        font: 85%/125% 'Lucida Grande', Verdana, Geneva, Lucida, Helvetica, Arial, sans-serif;
        letter-spacing: -1px;
}

.details {
        clear: both;
        margin: 15px 0 0 0;
        color: #111;
        font-size: 100%;
        font-weight : bold;
        text-align: center;
}

/* ----------------------------------------------
Legend Colour Scheme
---------------------------------------------- */
td#unchecked {
	background-color: #000033;
}

td#greenlight {
        background-color: #009900;
}

td#yellowlight {
        background-color: #FF9933;
}

td#redlight {
        background-color: red;
}

td#disabled {
        background-color: #999999;
}

.unchecked {
        color: #000033;
}

.greenlight {
        color: #009900;
}

.yellowlight {
        color: #FF9933;
}

.redlight {
        color: red;
}

.disabled {
        color: #999999;
}


/* ----------------------------------------------
Basic XHTML styling
---------------------------------------------- */

h1 {
	color: #666;
	font-size: 200%;
	font-family: 'Lucida Grande', Verdana, Geneva, Lucida, Helvetica, Arial, sans-serif;
	font-weight : bold;
	text-align : left;
}

h2 {
	font-size: 120%;
	font-weight: bold;
}

h3{
	font-size: 110%;
}

p, li, .feedback {
	font: 85%/125% 'Lucida Grande', Verdana, Geneva, Lucida, Helvetica, Arial, sans-serif;
	letter-spacing: -1px;
}

/* ----------------------------------------------
Links styling
Remember LoVe-HAte rule
---------------------------------------------- */
a {
	color: #036;
    text-decoration: none;
}

a:link {
	font-weight: bold;
}

a:visited {
	font-weight: bold;
}

a:hover {
	color: #900;
    text-decoration: underline;
}

a:active {
	text-decoration: underline overline;
}

a img {
	border: none;
}
	

/* ----------------------------------------------
Form styling
---------------------------------------------- */
form {
	margin: 0;
	padding: 0;
}
	
input, textarea {
	background-color: #eee;
	border: 1px solid #aaa;
	font-size:85%; 
}

http://www.ryanclark.org/cgi-bin/viewcvs.cgi/sites/org/ryanclark/www/cgi-bin/mon.cgi

http://www.ryanclark.org/cgi-bin/viewcvs.cgi/sites/org/ryanclark/www/moncgi.css