Here is a standard Theme's style sheetWith Comments

/* This controls the default settings on a page */
body {color: black; background: white; margin: 0px; padding: 0px;}

/* The default settings for ALL tables on a site, unless explicity defined for a particular table */
table {width: 100%; margin: 5px; padding: 5px; font-size: small}
table td {padding: 0px; border-width: 0px; vertical-align: top; font-family: Verdana, Arial, Helvetica, sans-serif;}

/* This controls the default link settings & link mouseover/hover settings */
a {color: #666666; text-decoration: none; font-weight: bold; background-color: transparent;}
a:hover {color: #ff6600;}

/* Controls HTML tags for headings #1-5, unordered list and items in the list */
h1 {4}
h2 {3}
h3 {9}
h4 {2}
h5 {1}
ul { margin: 2px; padding: 2px; list-style: decimal inside; text-align: left;}
li { margin-left: 2px; list-style: square inside; color: #2F5376}

/* Selector for a form button */

input.formButton {}

/* The following appear to primarily apply to the NEWS stories, */
/* though they may be found in other areas as well */
/*
BEGIN NEWS SECTION DEALING PRIMARILY WITH NEWS
*/

/* The border around news stories */
.item {border: 1px solid #cccccc;}

/* The BG color for the cell for news story titles */
.itemHead {padding: 3px; background-color: #2F5376; color: #FFFFFF;}

/* The BG color for the area right under a news title (post by so-and-so) */
.itemInfo {text-align: right; padding: 3px; background-color: #efefef;}

/* The text in the story title EXCEPT the colon between the topic and the title */
.itemTitle a {font-size: 130%; font-weight: bold; font-variant: small-caps; color: #ffffff; background-color: transparent;}

/* The text "exta6sy" just preceding the posters name */
.itemPoster {font-size: 90%; font-style:italic;}

/* The text On $date $time immediately after the posters name */
.itemPostDate {font-size: 90%; font-style:italic;}

/* The xx # reads for a story, but NOT the parenthesis surrounding the total */
.itemStats {font-size: 90%; font-style:italic;}

/* The text of the story itself */
.itemBody {padding-left: 5px;}

/* XOOPS DEVELOPER HELP NEEDED - This seems to be the same as .itemBody above. What is the difference??? */
.itemText {margin-top: 5px; margin-bottom: 5px; line-height: 1.5em;}

/* Makes the first letter in a story bold */
.itemText:first-letter {font-size: 133%; font-weight: bold;}

/* The foooter of a new story (read more, etc.) */
.itemFoot {text-align: right; padding: 3px; background-color: #efefef;}

/* The [edit | delete] section of a news footer */
.itemAdminLink {font-size: 90%;}

/* The | xx# bytes more | section of the news footer */
.itemPermaLink {font-size: 90%;}

/*
END SECTION DEALING PRIMARILY WITH NEWS
*/

/* Controls the settings for a table header */

th {background-color: #2F5376; color: #FFFFFF; padding : 2px; vertical-align : middle; font-family: Verdana, Arial, Helvetica, sans-serif;}

/* The area at the top of the page where the logo and advertising banner are */

td#headerbanner {width: 100%; background-color: #2F5376; vertical-align: middle; text-align:center;}

/* The whitish-grey bar on the default install right underneath the top section/header */

td#headerbar {border-bottom: 1px solid #dddddd; background-image: url(hbar.gif);}

/*
BEGIN SECTION DEALING WITH THE THREE COLUMNS
*/

/* controls the settings for blocks on the LEFT side of the page */
td#leftcolumn {width: 170px; border-right: 1px solid #cccccc; font-size:12px;}

/* controls the settings for the table headers on the left column */
td#leftcolumn th {background-color: #2F5376; color: #FFFFFF; vertical-align: middle;}

/* controls the settings for the block titles on the left column */
td#leftcolumn div.blockTitle {padding: 3px; background-color: #dddddd; color: #639ACE; font-weight: bold;}

/* controls the settings for the blocks' content on the left column */
td#leftcolumn div.blockContent {padding: 3px; line-height: 120%; line-height: 120%;}

/* controls the settings for block in the CENTER section of the page */
td#centercolumn {font-size: 12px;}

/* controls the settings for the table headers on the center column */
td#centercolumn th {background-color: #2F5376; color: #FFFFFF; vertical-align: middle;}

/* Controls the settings for "center-aligned CENTER blocks" on the page */
td#centerCcolumn {padding: 0px 3px 1px 3px;}
/* The title for center center blocks */
td#centerCcolumn legend.blockTitle {padding: 3px; color: #639ACE; font-weight: bold; margin-top: 0px; margin-right: 0px; margin-left: 0px;}
/* The content for center center blocks */
td#centerCcolumn div.blockContent {border-left: 1px solid #cccccc; border-right: 1px solid #cccccc; border-bottom: 1px solid #dddddd; padding: 3px; margin-right: 0px; margin-left: 0px; margin-bottom: 2px; line-height: 120%;}

/* Controls the settings for "left-aligned CENTER blocks" on the page */
td#centerLcolumn {width: 50%; padding: 0px 3px 0px 0px;}

/* The title for left-aligned center blocks*/
td#centerLcolumn legend.blockTitle {padding: 3px; color: #639ACE; font-weight: bold; margin-top: 0px;}

/* The content for left-aligned center blocks */
td#centerLcolumn div.blockContent {border-left: 1px solid #cccccc; border-right: 1px solid #cccccc; border-bottom: 1px solid #dddddd; padding: 3px; margin-left: 3px; margin-right: 2px; margin-bottom: 2px; line-height: 120%;}

/* Controls the settings for "right-aligned CENTER blocks on the page */
td#centerRcolumn {width: 50%; padding: 0px 3px 0px 0px;}

/* The title for right-aligned center blocks */
td#centerRcolumn legend.blockTitle {padding: 3px; color: #639ACE; font-weight: bold; margin-top: 0px;}
/* The content area for left-aligned center blocks */
td#centerRcolumn div.blockContent {border-left: 1px solid #cccccc; border-right: 1px solid #cccccc; border-bottom: 1px solid #dddddd; padding: 3px; margin-left: 2px; margin-right: 3px; margin-bottom: 2px; line-height: 120%;}

/* Controls everything defined as content. for example in news it controls: */
/* The article text, posted by, date, time & number of reads Including the parenthesis */
/* the [ | ] brackets around the admin edit section and also the disclaimer: "the comments are */
/* owned by the poster. We aren't responsible for their content" on the bottom of a news comments page */
/* also a ton of text on the forum page...probably a ton of stuff everywhere...be careful with this one */

div#content {text-align: left; padding: 8px;}


/* settings for blocks in the RIGHT column on a page*/
td#rightcolumn {width: 170px; border-left: 1px solid #cccccc; font-size:12px;}

/* Controls the table headers for the right columns.*/
td#rightcolumn th {background-color: #2F5376; color: #FFFFFF; vertical-align: middle;}

/* Controls the right column blocks' titles */
td#rightcolumn div.blockTitle {padding: 3px; background-color: #dddddd; color: #639ACE; font-weight: bold;}

/* Controls the right column blocks' content area */
td#rightcolumn div.blockContent {padding: 3px; line-height: 120%;}

/* END SECTION DEALING WITH THREE COLUMNS */

/* settings for the footerbar where the xoops copyright notice is */
tr#footerbar {text-align:center; background-image: url(hbar.gif);}

/* settings for the Main Menu */
td#mainmenu a {background-color: #e6e6e6; display: block; margin: 0px padding: 4px;}

/* What happens on a mouse hover on the main menu */
td#mainmenu a:hover {background-color: #ffffff;}

/* The top cell on the main menu (typically HOME). This way you can give the top cell a different border or */
/* other appearance. Useful for drawing a box around the entire menu, for instance. */
td#mainmenu a.menuTop {padding-left: 3px; border-top: 1px solid silver; border-right: 1px solid #666666; border-bottom: 1px solid #666666; border-left: 1px solid silver;}

/* The remaining entries in the main menu other than the top most defined one line above */
td#mainmenu a.menuMain {padding-left: 3px; border-right: 1px solid #666666; border-bottom: 1px solid #666666; border-left: 1px solid silver;}

/* The settings for submenu items that open when u are in a particular module. For example */
/* "Submit news" and "Archives" when you are on the news module */
td#mainmenu a.menuSub {padding-left: 9px; border-right: 1px solid #666666; border-bottom: 1px solid #666666; border-left: 1px solid silver;}

/* settings for the User Menu */
td#usermenu a {background-color: #e6e6e6; display: block; margin: 0px padding: 4px; border-right: 1px solid #666666; border-bottom: 1px solid #666666; border-left: 1px solid silver;}

/* What happens on a mouse hover on the user menu */
td#usermenu a:hover {background-color: #ffffff;}

/* The top most entry on the user menu */
td#usermenu a.menuTop {border-top: 1px solid silver;}

/* The settings for when a user has a private message */
td#usermenu a.highlight {background-color: #fcc;}


/* Styles used to draw homogeneous tables */
/* Described in a seperate page in the xoops.org wiki */
.outer {border: 1px solid silver;}
.head {background-color: #c2cdd6; padding: 5px; font-weight: bold;}
.even {background-color: #dee3e7; padding: 5px;}
.odd {background-color: #E9E9E9; padding: 5px;}
.foot {background-color: #c2cdd6; padding: 5px; font-weight: bold;}
tr.even td {background-color: #dee3e7; padding: 5px;}
tr.odd td {background-color: #E9E9E9; padding: 5px;}

/* NOT INCLUDED IN DEFAULT */
/* customization to add special color to forum title head. requires editing newbb_index.html template as well */
.outerhead{}
.outerhead a{font-size: 12px; color : #FFFFFF;}
.outerhead a:hover{}

/* NOT SURE Special system messages MAYBE */
/* I leave the defaults */
div.errorMsg { background-color: #FFCCCC; text-align: center; border-top: 1px solid #DDDDFF; border-left: 1px solid #DDDDFF; border-right: 1px solid #AAAAAA; border-bottom: 1px solid #AAAAAA; font-weight: bold; padding: 10px;}
div.confirmMsg { background-color: #DDFFDF; color: #136C99; text-align: center; border-top: 1px solid #DDDDFF; border-left: 1px solid #DDDDFF; border-right: 1px solid #AAAAAA; border-bottom: 1px solid #AAAAAA; font-weight: bold; padding: 10px;}
div.resultMsg { background-color : #CCCCCC; color: #333333; text-align: center; border-top: 1px solid silver; border-left: 1px solid silver; font-weight: bold; border-right: 1px solid #666666; border-bottom: 1px solid #666666; padding: 10px;}

/* Settings for when you insert code in a forum post */
div.xoopsCode { background: #FFFFFF; border: 1px inset #000080; font-family: "Courier New",Courier,monospace; padding: 0px 6px 6px 6px;}
/* Settings for when you quote during a forum post */
div.xoopsQuote { background: #FFFFFF; border: 1px inset #000080; font-family: "Courier New",Courier,monospace; padding: 0px 6px 6px 6px;}


/* Styles for the commenting system */
.comTitle {font-weight: bold; margin-bottom: 2px;}
.comText {padding: 2px;}
.comUserStat {font-size: 10px; color: #2F5376; font-weight:bold; border: 1px solid silver; background-color: #ffffff; margin: 2px; padding: 2px;}
.comUserStatCaption {font-weight: normal;}
.comUserStatus {margin-left: 2px; margin-top: 10px; color: #2F5376; font-weight:bold; font-size: 10px;}
.comUserRank {margin: 2px;}
.comUserRankText {font-size: 10px;font-weight:bold;}
.comUserRankImg {border: 0px}
.comUserName {}
.comUserImg {margin: 2px;}
.comDate {font-weight: normal; font-style: italic; font-size: smaller}
.comDateCaption {font-weight: bold; font-style: normal;}