This file defines a framework and a guidline that describes, what things
a theme must contain, how the naming-convention is, etc.

All themes are stored in own sub-directories in the directory 'themes'.


A theme must contain at least the following files :
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* styles_800.css : A stylesheet for a screen-resolution of 800x600.

* styles_1024.css : A stylesheet for a screen-resolution of 1024x768.

* next.png, prev.png, first.png, last.png, note.png : Images for the
        previous-, next-, first-, last- and note-button. They must have a
        transparent background, because the background-color (or -image) of
        the slide must not interfer with the background-color of the button.

* config : A configuration-file. Until now, this config-file doesn't contain
        any data. But if it doesn't exist, PresTiMeL will not recognize the
        theme.

* bg_slide.jpg : The background-image (or -tile) for the whole slide.

* bg_header_800.png : The background-image for the header (800x600).

* bg_header_1024.png : The background-image for the header (1024x768).


The following tags must be defined in the stylesheets :
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
* The background for the slides
  - body.graphic : Defines the background-image for all slides.
  - body.color : Defines the background-color for all slides.

* The headline
  - div.header : Defines the top- and bottom-margin of the header.
  - td.header : Defines the background-image for the header.
  - h1 : Defines the font-size, -family and -align for the headline.
  - a.header : Defines the color of the headline.
               It's recommendet to define the attribute "text-decoration:none",
               so the headline (a hyperlink to the index) won't be underlined.

* The Title-environment 
  - h2,h3 : Defines the font-size, -family, -color and -align for the texts.
            Bottom, left and right margins may also be given.
  - p.author : Defines the font-size, -family and alignment of the authors.
  - a:link : Defines the font-color of the authors, which are hyperlinks to
             the e-mail addresses.
  - p.date : Defines the font-size, -color, -family and alignment of the date.

* The list-environments :
  - div.listtiny : Defines a big left margin.
  - div.listmedium : Defines a medium left margin.
  - div.listlarge : Defines a small left margin. For cosmetical reasons there
                    should be also defined a small right margin.
  - li.itemnormal, p.itemnormal : Defines the font-size, -family and -color
                                  for normal items.
  - li.itemweak, p.itemweak : Defines the font-size, -family and -color for
                              weak items.

* The Code-environment :
  - div.code : Defines the left margin for a stand-alone code-environment.
  - pre.code : Defines the font-size, -family and -color for the code.
               The use of a monospaced font like Courier is recommendet.

* The Text-environment :
  - div.text : Defines the left and right margin for a stand-alone
               text-environment.
  - p.text : Defines the font-size, -family and -color for the text.
  - code.text : Defines the font-size, -family and -color for monospaced text.

* The Footer :
  - div.footer : Defines the position of the footer, which contains the
                 navigation buttons. The position must be given absolute
                 from the top of the page, because no Web browser currently
                 supports margins from the bottom.
