Joomal en 5 minutos.

/* STANDARD COMPLETE CSS FOR JOOMLA 1.0.X and MAMBO 4.5.X TEMPLATES */ /* By Dinh Viet Hung (C) http://www.joomlart.com: Free templates and Professional Templates Club */     /* DEFAULT SETTINGS */  /* Below are  default settings are used when no other style has been defined.*/ body {}/*Style for the body tag of your website, controls font family page background, etc.*/ p {} /*formatting all <div> (division) items.  This is a catch-all that only applies when no other  style has been defined.*/ td {} /*formatting all  <td> items. This default setting is used when no other style has been defined.*/ tr {} /*formatting all  <tr> items.  This default setting is used when no other style has been defined.*/ ul {} /*formatting all UL (unordered list) items. This default setting is used when no other style has been defined.*/ a:link {} /* general links style*/ a:visited {} a:hover {} hr {} /* horizontal line in your template*/ hr.separator {}   /* FORMS SETTINGS */  .button {} .inputbox {} .search {} /*formatting the <div> which holds search items: inputbox, search button...*/     /* NAVIGATION/MENU SETTINGS */   a.mainlevel{} /* this styling is for the MAIN items in the menu */ a.mainlevel:link {} a.mainlevel:visited {} a.mainlevel:hover {}   #active_menu {} /* this styling is for the menu item when it is active, even in main/sub position*/   ul#mainlevel-nav {} ul#mainlevel-nav li{} #mainlevel-nav a:link {} #mainlevel-nav a:visited{} #mainlevel-nav a:hover {}   a.sublevel{} /* this styling is for menu items that HAS A PARENT */ a.sublevel:link {} a.sublevel:visited {} a.sublevel:hover {}   .pagenavbar {} /*Sets the style for the footer navigation ("<< Start < Prev Next > End >>")  when they do not appear as hyperlinks (when only a few articles exist).*/ .pagenavbar:link {} /*Style for the footer navigation ("<< Start < Prev Next > End >>") when  they become hyper links*/ .pagenavbar:visited {}   .pagenav {} /* as the name implies, this is for formatting texts for those  "<< Start < Previous 1 Next > End >>" links */ a.pagenav:visited {} a.pagenav:hover {}   a.readon:link {} /*Style for the "Read More" link that is displayed for large content items*/ a.readon:hover {} a.readon:visited {}   .back_button {} /*Style for the "BACK" button*/ .pagenav_prev {} /*Style for the PRE button*/ .pagenav_next {} /*Style for the NEXT button*/   .latestnews ul {} /*Style for latest news list - by default, latest news is user1 module*/ .latestnews li {}   .mostread ul{} /*Style for most popular list - by default, most popular is user2 module*/ .mostread li{}   /* CONTENT PAGE SETTINGS */ a.category:link {} a.category:hover {} a.category:visited {}   .blogsection {} /* Formatting the links in Blog section */ .blog_more {} /*The "More" text in blog section*/ a.blogsection:link {} /* set the link format */ a.blogsection:visited {} /* same as above, but to set the visited link format */ a.blogsection:hover {} /* same as above, but for links with mouse pointer over it */   .componentheading {}/* Title of the component being used to display the content.*/ .contentheading {} /* Title of the content, article, etc. being displayed.*/ .contentpane {} /* Table that holds all non-article information (components,  category lists, contact forms, etc).*/ .contentpaneopen {} /* Table that holds the actual text for an article.*/ .contentpagetitle {} /*Title of articles*/   a.contentpagetitle:hover {} /*Title of articles when appeare as links */ a.contentpagetitle:link {} a.contentpagetitle:visited {}   .contentdescription {} /* Formating the "DESCRIPTION" of sections, categories  (News/Weblinks/Latest news...) */ table.contenttoc {} /* Formating the table of the Tables of Contents for multiple  pages content or article */ table.contenttoc td {} /* same as above, used to format the td and able cells */ table.contenttoc th {} /* same as above, used to format the th of "Tables of  Content" ( normally Article Index)*/ table.contenttoc td.toclink {} /* same as above, used to format toc link texts*/ a.toclink:link {} /* same as above, used to format toc link text status*/ a.toclink:visited {}  a.toclink:hover {}      /* JOOMLA - MAMBO SECTIONS LISTINGS */ .sectiontableheader {} /* This is for styling the section table headers on a  SECTION's page. Example: table header of "Date", "Item Title", "Author" and "Hits"? */ .sectiontableentry1 {}  .sectiontableentry2 {}     /* JOOMLA - MAMBO MODULES FORMATTING */ table.moduletable {} /* Formatting the module table */ table.moduletable th {} /* Formatting the module header, and the module titles */ table.moduletable td {} /* Formatting the table cells of the module table */     /* MISCELLANEOUS */   /* Dates , Authors*/ .createdate {} /* For styling the date the content/articles are created under contents title */ .modifydate {} /* Formating "Last updated on" text at the end of articles/contents */ .small {} /* Formating "Written by:...." text */ .smalldark {}/*Found in poll result page, for " Number of Voters".. text */   /* Polls */ .poll {} /* format the td of poll table */ .pollstableborder {} /* set the border properties of the polls voting table */     /* Weblinks */ .weblinks{} /* well.. to format the link's titles under the "Weblinks"    section on the frontend */ a.weblinks:hover {} /* same as above, but for link with mouseover */   /* Newsfeeds */ .newsfeedheading {} /* The newsfeed title. NOTE: This will not affect the newsfeed's news title! */ .newsfeeddate {} /* yeah.. the date on the newsfeed */ .fase4rdf {} /* this is the body text of the newsfeed */   /* Search page */ table.searchintro {} /* This is for formatting the box with "Search Keyword: test returned 4 matches" box that appears after you have entered a search value. It appears on the mainbody with the search results */     /* JOOMLA - MAMBO TABBED FRONTEND ADMIN INTERFACE */ /* The CSS below efines how the frontend admin interface when logged in */   .ontab {}/* For styling of the "Tab" buttons when editing contents through the  frontend as admin.  This .ontab is the styling for the tab when it is active or after its "clicked" */ .offtab {} /* Same as above, used for styling of the "Tab" buttons when editing  contents through the frontend.  This the styling for the tab when it is NOT active or when it is NOT "clicked" */ .tabpadding {} /* this style is used set the size of the tab in the above */  .tabheading {} /* Not too sure what this is used for. Couldn't find anything  related to it yet at the moment */ .pagetext {} /* this style is used to style the content of the editing form  contents (where HTMLArea sits and all its forms + contents) in the frontend  Administration interface */

4. Joomla / Mambo Template CSS: Tweaking and Tuning
Normally, you tend to make your template look match with your site contents or just want to make it distinguished from the others. Therefore, playing around with your css file is the most popular practice of Joomla / Mambo users. The file you have just download is not filled with any style at all. If you do not want to start from scratch or feel un familiar with css styling, you can open another template_css.css file of any existing templates for css reference, copy and paste, make some changes and refresh to see how they affect your Jooma / Mambo site.
5. Is that all? 
template_css.css is just a part of Joomla / Mambo templating job. CSS defines content elements your Joomla / Mambo pages. Layout and modules navigation of your template are also important. Details of Joomla / Mambo layout are also picturized and well explained in this tutorial: Joomla / Mambo layout and navigation guides.
Hope you enjoy reading.