GIF

The Graphics Interchange Format (better known by its acronym GIF /ˈdʒɪf/ JIF or /ˈɡɪf/ GHIF) is a bitmap image format that was introduced by CompuServe in 1987 and has since come into widespread usage on the World Wide Web due to its wide support and portability.

The format supports up to 8 bits per pixel for each image, allowing a single image to reference its own palette of up to 256 different colors chosen from the 24-bit RGB color space. It also supports animations and allows a separate palette of up to 256 colors for each frame. These palette limitations make the GIF format less suitable for reproducing color photographs and other images with continuous color, but it is well-suited for simpler images such as graphics or logos with solid areas of color.

GIF images are compressed using the Lempel-Ziv-Welch (LZW) lossless data compression technique to reduce the file size without degrading the visual quality. This compression technique was patented in 1985. Controversy over the licensing agreement between the software patent holder, Unisys, and CompuServe in 1994 spurred the development of the Portable Network Graphics (PNG) standard. By 2004 all the relevant patents had expired.

Web beacon

A web beacon is an object embedded in a web page or email, which unobtrusively (usually invisibly) allows checking that a user has accessed the content. Common uses are email tracking and page tagging for web analytics. Alternative names are web bug, tracking bug, tag, or page tag. Common names for web beacons implemented through an embedded image include tracking pixel, pixel tag, 1×1 gif, and clear gif. When implemented using JavaScript, they may be called JavaScript tags. There is a work in progress to standardize an interface that web developers can use to asynchronously transfer small HTTP data from the User Agent to a web server that call it simply beacons (in the context of web development) which can be used to send data to a web server prior to the loading of the document without delaying the load and affecting the perception of page load performance for the next navigation.

Overview

A web beacon is any of a number of techniques used to track who is reading a web page or email, when, and from which computer. They can also be used to see if an email was read or forwarded to someone else, or if a web page was copied to another website. The first web beacons were small images.

Intrinsic factor

Intrinsic factor (IF), also known as gastric intrinsic factor (GIF), is a glycoprotein produced by the parietal cells of the stomach. It is necessary for the absorption of vitamin B₁₂ (cobalamin) later on in the small intestine. In humans, the gastric intrinsic factor protein is encoded by the GIF gene.

Haptocorrin (also known as HC, R protein, and transcobalamin I, TCN1), is a glycoprotein secreted by the salivary glands which binds to vitamin B₁₂. Vitamin B₁₂ is acid sensitive and in binding to transcobalamin I it can safely pass through the acidic stomach to the duodenum. Here in the less acidic environment of the small intestine, pancreatic enzymes digest the glycoprotein carrier and vitamin B₁₂ can then bind to intrinsic factor. This new complex is then absorbed by the epithelial cells (enterocytes) of the ileum. Inside the cells, B₁₂ dissociates once again and binds to another protein, transcobalamin II (TCN2). The new complex can then exit the epithelial cells to be carried to the liver.