Web's were implanted in everyone's head starting at age 7. They had to be adjusted as they grew and their brain changed. This allowed everyone to access the Net with just a thought. If they thought something all of the information became instantly available.
|[...]Earth data net with a single thought, search through the accumulated knowledge of humanity, and view thousands of images directly with his brain[...]|
–narrative , 
By the middle of the 24th century (half way through Exodus Century) Earth could no longer manufacture new webs
|[...]It was the first technology to be lost because of experts leaving for other worlds, and the first warning sign that Earth’s infrastructure was falling apart.|
Webs needed to be tuned every year to compensate for the changes in the brain. Not only were the experts for implanting the webs but Earth didn't have enough experts to manufacture the equipment to tune the webs nor the experts to do the tuning.
Because the webs weren't tuned, people started to lose their connections to web which caused a tremendous amount of anguish. Then came the Suicide Decade when the webs were breaking down and people couldn't adjust.
Scavenger Exodus Series
Tad is the last human to be webbed and it had to be done with a salvaged web taken from a dead child. The reason that his grandfather insisted that he be webbed was because he needed to recreate portal technology that could be manufactured after the existing ones started failing due to age.
Earth Girl Series References
This is the only reference to being Webbed in the Earth Girl books, it is mentioned and becomes important in the Scavenger Exodus Series.
|Central to the twenty-third century society was an individual’s personal net,” said our teacher. “These were completely invisible to anyone else, since there was no actual display. You saw your personal net by means of signals sent directly to the visual centre of your brain.|
- Edwards, Janet. Scavenger Alliance (Scavenger Exodus Book 1) (p. 129). Wallam-Crane Press. Kindle Edition.
- Edwards, Janet. Earth and Fire: An Earth Girl Novella (EGN Book 1) (p. 95). Wallam-Crane Press. Kindle Edition.