Writing for the Web: A Primer for Librarians

by Eric H. Schnell

Graphics and Images

The appropriate role of graphics and images in HTML documents is a point of debate among Web authors. While inserting graphics can make a document visually appealing to the user, the size and the number of graphic images can also detract from the content. The proper use of graphics can determine whether a patron will visit again.


There are two main types of images which can be used in Web documents, "in-line"and "external." In-line images are embedded within the Web document and are automatically displayed by the Web browser. The HTML tag used to include an inline image is <IMG SRC>, (IMaGe SouRCe). The syntax used is identical to that used in the tag <A HREF> with the file location encoded using a relative or absolute pathname. To include the colorful paragraph break above into this HTML document the following HTML code was used: <IMG SRC="/images/rainline.gif">

Picture of Head

External images are those which are independent of a Web document and need to be consciously downloaded by the user. In-line images, such as the one to the left, may lead to the larger external images. To include this linked image into this HTML document the following HTML code was used: <a href = "head.jpg"><img align=left src = "head_small.gif">

In some instances these images are not immediately recognizable by your browser, requiring additional software (helper applications). When a browser encounters an image it can not display, it starts the independent helper application to display the image. Most helper applications are available as Web browser "plug-ins" and integrate the secondary program into the browser window

File Formats

There are many different file formats available for images. The two most common formats, both used in the above examples, are GIF (pronounced with a hard G by some, "jiff" by others) or JPEG ("jay-peg"). A newer format, called the Portable Network Graphic (PNG or "ping") is also under development. PNG is designed to work in online viewing applications like the Web. FlashPix is another format designed with the Internet in mind. Developed by Kodak, this format is intended to transfer and display high definition images quickly across the Web.

The type of image being viewed, or to be viewed, can be identified by a three letter Multipurpose Internet Mail Extension (MIME). The extensions for the aforementioned formats are .gif and .jpg. Web browsers use the MIME extensions to identify the format and to determine which helper application, if any, is needed.



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Page Updated: Tuesday, 24-Nov-98