Administrative -- Technical -- Historical
addressing -- extensions -- naming -- construction
Web Extensions, or File Formats
PDF - (Portable Document Format) Created by Adobe Systems in its software program Adobe Acrobat as a universal browser. Files can be downloaded via the web and viewed page by page, provided the user is computer has installed the necessary plug-in which can be downloaded from Adobe's own web site.
GIF - (Graphic Interchange Format) works best with line art and spot-color (illustrations, cartoons, logos), supports transparancy, interlacing and animation
JPG - (Joint Photographic Experts Group) works best with photographs, and images with subtle gradations.(do not "re-compress" a jpg, always make changes to the original file and recompress from there;) Does not support transparency or animation.
PNG - (Portable Network Graphics) and is generally pronounced "ping." PNG is used for lossless compression and displaying images on the web. The advantage of PNG is that it supports images with millions of colors and produces background transparency without jagged edges. The disadvantages are that PNG images will not show up on older browsers, and still can be comparatively larger in file size than GIFs.
HTML or HTM - (Hypertext Markup Language) a web page