A polygraph (commonly referred to as a lie detector) is an instrument that measures and records several physiological responses such as blood pressure, pulse, respiration and skin conductivity while the subject is asked and answers a series of questions. The polygraph measures physiological changes caused by the Sympathetic Nervous System during questioning. Within the Federal Government, a polygraph examination is also referred to as a psychophysiological detection of deception (PDD) examination.

A polygraph (commonly referred to as a lie detector) is an instrument that measures and records several physiological responses such as blood pressure, pulse, respiration and skin conductivity while the subject is asked and answers a series of questions. The polygraph measures physiological changes caused by the Sympathetic Nervous System during questioning. Within the Federal Government, a polygraph examination is also referred to as a psychophysiological detection of deception (PDD) examination.

The idea that lying produces physical side-effects has long been claimed. In West Africa persons suspected of a crime were made to pass a bird's egg to one another.If a person broke the egg, then he or she was considered guilty, based on the idea that their nervousness was to blame. In Ancient China the suspect held a handful of rice in his or her mouth during a prosecutor's speech. Since salivation was believed to cease at times of emotional anxiety, the person was considered guilty if by the end of that speech the rice remained dry.

The origins of the modern polygraph date to 1913, when William Moulton Marston, a psychology student at Harvard University, used the systolic blood-pressure test as a method of lie detection. In his book, the "lie detector test" Marston erroneously claimed he was the first to use this method, even though many researchers were doing similar studies. He wrote a second paper on the concept in 1915, when finishing his undergraduate studies. He entered Harvard Law School and graduated in 1918, re-publishing his earlier work in 1917. A more complex device recording both blood-pressure and galvanic skin response was invented by Dr. John A. Larson of the University of California and first applied in law enforcement work by the Berkeley Police Department under its nationally renowned police chief August Vollmer. The first time the term "polygraph" was used was in 1908 by James MacKenzie in his invention the "ink polygraph," which was used for medical reasons.

Marston nevertheless remained the device's primary advocate, endlessly lobbying for its use in the courts. In 1938 he published a book, The Lie Detector, where he documented the theory and use of the device. Nevertheless he was not above a little faked publicity, and in 1938 appeared in advertising by the Gillette company claiming that the polygraph showed Gillette razors were better than the competition.

When polygraphs are used as a screening tool (in national security matters and for law enforcement agencies for example) the level of accuracy drops to such a level that “Its accuracy in distinguishing actual or potential security violators from innocent test takers is insufficient to justify reliance on its use in employee security screening in federal agencies.” In fact, the NAS extrapolated that if the test were sensitive enough to detect 80% of spies (a level of accuracy which it did not assume), in a hypothetical polygraph screening of 10,000 employees including 10 spies, 8 spies and 1,598 non-spies would fail the test. Thus, roughly 99.6 percent of positives (those failing the test) would be false positives. The NAS concluded that the polygraph “…may have some utility” but that there is "little basis for the expectation that a polygraph test could have extremely high accuracy."

The NAS conclusions paralleled those of the earlier United States Congress Office of Technology Assessment report "Scientific Validity of Polygraph Testing: A Research Review and Evaluation”.

It is shaky at best to determine a polygraph's effectiveness in regards to detection and/or deterrance of spying. Failure of a polygraph test could cause revocation of a security clearance, but it is inadmissable evidence in most federal courts and military courts martials. In most cases, however, polygraphs are more of a tool to "scare straight" those who would consider espionage.

Although it took time for the PNG format to be supported, new web browsers support the PNG format and GIF images can usually be replaced by PNG images if desired. However, Internet Explorer versions 6 and earlier do not support PNG's alpha channel transparency feature without using Microsoft-specific HTML extensions. Using standard HTML tags for PNG images in Internet Explorer can produce a look different from that intended. Internet Explorer 7 supports alpha channel transparency without needing extensions.

There have been claims that PNG files are generally larger than GIFs. PNG files can indeed be much larger than GIF files in situations where a GIF and a PNG file were created from a high-quality master image, as  PNG is capable of storing more color depth and transparency information than GIF. However, identical 8-bit  (or lower) image data rendered in PNG and GIF formats should yield similar sizes. Misinformation about PNG efficiency can generally be traced back to poor PNG support in older versions of some image manipulation programs, (for example Adobe Photoshop did not optimize PNGs for reduced color palettes by  default.

Tagged Image File Format (abbreviated TIFF) is a container format for storing images, including photographs and line art. It is now under the ownership of Adobe. Originally created by the company Aldus for use with what was then called "desktop publishing," TIFF is a popular format for color and black and white images. The TIFF format is widely supported by image-manipulation applications, by publishing and page layout applications, by scanning, faxing, word processing, optical character recognition and other applications. Adobe Systems, which acquired Aldus, now holds the copyright to the TIFF specification. TIFF has not had a major update since 1992, though several Aldus/Adobe technical notes have been published with minor extensions to the format, and several specifications, including TIFF/EP, have been based on the TIFF 6.0 specification.

The phrase "Tagged Image File Format", or, actually, "Tag Image File Format", was used as a subtitle in some earlier versions of the TIFF specification. The current TIFF specification, TIFF 6.0, makes no mention of these phrases; the name is now, simply, "TIFF".

TIFF was originally created as an attempt to get desktop scanner vendors of the mid-1980s to agree on a common scanned image file format, rather than have each company promulgate its own proprietary format. In the beginning, TIFF was only a bi-level image format, since that was all that desktop scanners could handle. As scanners became more powerful, and as desktop computer disk space became more plentiful, TIFF grew to accommodate grayscale images, then color images.

TIFF is a flexible and adaptable file format. It can handle multiple images and data in a single file through the inclusion of "tags" in the file header. Tags can indicate the basic geometry of the image, such as its size, or define how the image data is arranged and whether various image compression options are used. For example, TIFF can be used as a container for JPEG and RLE (run-length encoding) compressed images. A TIFF file can also include a vector-based Clipping path (an outline that crops or frames the main image). The ability to store image data in a lossless format makes TIFF files a useful method for archiving images. Unlike standard JPEG, TIFF files using lossless compression (or no compression at all) can be edited and resaved without suffering a compression loss. Other TIFF file options include multiple layers or pages.