NCSA Mosaic for the X Window System User's Guide

## Some Basics

HTML-coded documents are called source files. Source files are in plain text format and can be created using any text editor (e.g., EMACS or vi on UNIX workstations). Several Web browsers (tkWWW for X Window System machines and CERN's Web browser for the NeXT) include rudimentary HTML editors in a WYSIWYG (what you see is what you get) environment, and you may want to try one of them. See ``Web Resources'' for more on HTML editors.

HTML tags consist of a left angle bracket (<), followed by some coding (called the directive), and closed by a right angle bracket (>). HTML tags are generally paired (e.g., <H1> and </H1>. The ending tag looks just like the starting tag except a slash (/) precedes the directive within the brackets. For example, <H1> tells the viewer to start formatting a top-level heading, and </H1> tells the viewer that the heading is complete.

HTML tags are inserted in the source files to tell NCSA Mosaic (or some other Web viewer) how to interpret or display the coded information. For example, citation tags are defined by NCSA Mosaic to be displayed in italics. Each time you enclose a book title between <cite> and </cite> tags, NCSA Mosaic automatically displays the text in italics. This is known as a logical style, because it is configured by the viewer. Viewers can interpret a logical style in different ways.

### Hyperlinks

The chief power of HTML comes from its ability to link regions of text (and also images) to another document (or an image, movie, or audio file). These regions are highlighted to indicate that they are hypertext links. To create a hyperlink, a special HTML code is entered that includes the URL (see ``The URL Format''). At the same time, text or a graphic is designated to serve as the anchor (the information that is displayed in color or underlined and clicked on). A hyperlink may be made to a remote or local server.

### Images

NCSA Mosaic can display images inside documents, making it a highly visual medium for your information. However, each image requires processing time, which slows down the initial display of the document. Using a particular image multiple times in a document causes very little performance degradation compared to using the image only once.

An image is sized before it is included in a document. Images can fill a screen or they can be ``postage stamps'' -- small images that save time when NCSA Mosaic displays the document but are still large enough to present information and be a teaser for the larger image displayed in a separate window.

An image tag is coded into the source file to tell NCSA Mosaic that an image is to be displayed. The image tag is an HTML extension first implemented in NCSA Mosaic.