Although the fossil record of spiders is considered poor, almost 1000 species have been described from fossils. Because spiders' bodies are quite soft, the vast majority of fossil spiders have been found preserved in amber.

The oldest known amber that contains fossil arthropods dates from 130 million years ago in the Early Cretaceous period. In addition to preserving spiders' anatomy in very fine detail, pieces of amber show spiders mating, killing prey, producing silk and possibly caring for their young. In a few cases amber has preserved spiders' egg sacs and webs, occasionally with prey attached; the oldest fossil web found so far is 100 million years old. Earlier spider fossils come from a few lagerstatten, places where conditions were exceptionally suited to preserving fairly soft tissues.

It's a 49-million-year-old spider face - in 3-D   MSNBC - May 20, 2011

A very old spider has shown its face to the world for the first time in 49 million years, as scientists used high-tech X-ray methods to peer through the shroud of amber encasing the fossilized arachnid. These arachnids, also known as Huntsman spiders, live in the tropics and in Southern Europe today. From leg to leg, they can grow to a size of almost a foot. Huntsman spiders are non-aggressive and non-toxic to humans, but they can deliver a painful bite.

Largest Fossil Spider Found in Volcanic Ash   Live Science - April 20, 2011

The largest fossil spider uncovered to date once ensnared prey back in the age of dinosaurs, scientists find. The spider, named Nephila jurassica, was discovered buried in ancient volcanic ash in Inner Mongolia, China. Tufts of hairlike fibers seen on its legs showed this 165-million-year-old arachnid to be the oldest known species of the largest web-weaving spiders alive today - the golden orb-weavers, or Nephila, which are big enough to catch birds and bats, and use silk that shines like gold in the sunlight.

Oldest known spider's web found in amber   PhysOrg - November 2, 2009

  Ancient spiders yield 3D secrets   BBC - August 5, 2009
Ancient fossilized, spider-like species have been imaged in 3D using thousands of X-ray scans and imaging software.

  Ancient web spins evolution story BBC - June 22, 2006

The oldest-known spider web with prey still entrapped has been found preserved in a chunk of amber in Spain. The mesh of silk strands - snaring the remains of a fly, beetle, mite and wasp - dates back 110 million years to the time of the dinosaurs. The fossil web appears to have been designed along the same lines as the round nets woven by modern spiders. The find sheds light on the early evolution of spiders and the insects they fed on.

Early web-spinner found in amber BBC - June 14, 2006

Spiral orb webs, which to many people typify spiders, were catching insects in their sticky silk while the dinosaurs still walked the Earth. True orb weaving spiders found trapped in amber from 121-115 million years ago are the oldest of their type yet found. The spiral webs have proven an extremely successful strategy for catching prey - evidenced by the great diversity of orb weavers present today.

Spider blood found in 20 million year old fossil PhysOrg - September 30, 2005

Two droplets of blood, technically known as haemolymph, have been preserved in the amber which also contains the spider - Filistatidae - a family commonly found in South America and the Caribbean. The droplets are the first identified examples of spider blood ever found in an amber fossil. It is possible the blood could be used to extract DNA. The fossil, which is 4cm long and 2cm wide, was discovered in the Dominican Republic and dates back to the Miocene period.

Oldest spider silk preserved in amber BBC - August 7, 2003

A dinosaur-era spider web is found preserved in amber. The oldest known strand of spider silk has been found, preserved in Lebanese amber. It dates from the Early Cretaceous Period, more than 120 million years ago. This means it comes from about 80-90 million years further back in time than the previous oldest reported spider thread, found in Baltic amber.