Short answers, pulled from the story.
The first recorded appearance of Vikings occurred in the year 793 when armed men landed on Lindisfarne Island and attacked a Christian monastic community. This event marked the beginning of Viking history as documented by neighboring cultures.
Wood was undoubtedly the primary material of choice for Viking artists because it was relatively easy to carve, inexpensive, and abundant in northern Europe. Despite this preference, wood survives only rarely compared to metal or stone artifacts due to rapid deterioration over time.
The art historian Bernhard Salin was the first to systematise Germanic animal ornament by dividing it into three styles labeled I II and III. This classification formed the foundation upon which later subdivisions like Style C and Style D were developed.
Borre Style prevailed in Scandinavia from the late 9th through to the late 10th century according to dendrochronological data supplied from sites like Gokstad dated between 900 and 905 and Tune dated between 905 and 910. A more particular diagnostic feature lies in a symmetrical double-contoured ring-chain whose composition consists of interlaced circles separated by transverse bars and a lozenge overlay.
Mid-Urnes Style has received relatively firm dating based on coins issued by Harald Hardrada between 1047 and 1066 and by Olav Kyrre between 1080 and 1090. Two wood carvings from Oslo have been dated to around 1050 and 1100 while the Hørning plank is dated by dendrochronology to c. 1060 and 1070.