Mars Anomaly Research was the name of an internet cesspool of hysterical crankery that retained some popularity for a while before apparently dying away some time ago. Its main purpose was to show (well, assume) that NASA and ESA have been doctoring space image data from the get-go in order to cover up the truth that Mars and other bodies in the solar system are actually much more similar to the Earth than we are being told and contain several life forms and, indeed, advanced civilizations. Why NASA and ESA would do that is anyone’s guess, but conspiracy theorists would probably have no problem coming up with a feeble and incoherent explanation and zealously defend its accuracy in the face of any counter-evidence or reductio.
In any case, the site was maintained by one J. P. Skipper. His “evidence” consisted primarily of strange-shaped shadows that, with the right photoshopping, would look quite a bit like
facilitated pareidolia farms, buildings, giant trees, or deliberate airbrushing of notable features by
evil scientists. As for the conspiracy, Skipper seems mainly to have believed
that authorities actually believed that these other worlds were lifeless and
only doctored the images passed to the public to make sure no one started
questioning their cherished theories.
Most of the “evidence” was ridiculously poor examples of, well, pareidolia. Some “images” of various planets were not photos of planets at all, but digital models that Skipper would mistake for photos (e.g. here). In general Skipper and his fans displayed a pretty poor understanding of how scientific instruments taking photos of things millions of miles away actually work. See here for an example of “forest life on Mars”.
Diagnosis: While “bullshit” is probably a more apt characterization than “deliberate misleadings”, the website at least contained quite an impressive amount of it. Though the site has been down for a while (leading to all sorts of conspiracies over at Above Top Secret, Skipper might be back with more of it before you know.