This refers to the location of the Home Assistant server. If Cathedral is running on a device that is on the same network as the Home Assistant Server, then a "local network" http:// URL is most likely needed. For example, http://homeassistant.local:8123. If the Home Assistant Server is on a different network than Cathedral, then an "internet" https:// URL is most likely needed. Both of these URLs can be found in Home Assistant under Settings | Server | Network.

In order for Cathedral to communicate, it must first be authorized. A Long-Lived Access Token can be generated from within Home Assistant under Account | Long- Lived Access Tokens.

Any valid CSS "background" property can be used here. Any standard CSS colors can be used directly, like red or purple. Hex colors can be specified using either #FFF or #FFFFFF. RGB colors can be specified using rgb(40,0,0). Images can be specified using url(local filename) or url(any valid URL). Gradients can also be used.

y	= Year last 2 digits
yy	= Year last 2 digits
yyyy	= Year as 4 digits
m	= Month number no-leading 0
mm	= Month number as 2 digits
mmm	= Month using ShortDayNames (Jan)
mmmm	= Month using LongDayNames (January)
d	= Day number no-leading 0
dd	= Day number as 2 digits
ddd	= Day using ShortDayNames (Sun)
dddd	= Day using LongDayNames  (Sunday)
ddddd	= Day in ShortDateFormat
dddddd	= Day in LongDateFormat
c	= Use ShortDateFormat + LongTimeFormat
h	= Hour number no-leading 0
hh	= Hour number as 2 digits
n	= Minute number no-leading 0
nn	= Minute number as 2 digits
s	= Second number no-leading 0
ss	= Second number as 2 digits
z	= Milli-sec number no-leading 0s
zzz	= Milli-sec number as 3 digits
t	= Use ShortTimeFormat
tt	= Use LongTimeFormat
am/pm	= Use after h : gives 12 hours + am/pm
a/p	= Use after h : gives 12 hours + a/p
ampm	= As a/p but TimeAMString,TimePMString
/	= Substituted by DateSeparator value
:	= Substituted by TimeSeparator value

Reference: http://www.delphibasics.co.uk/RTL.php?Name=formatdatetime