While a work in progress, this article is not deemed fully reliable.
A webbed character is unable to perform most actions, including movement and speech, and receives a penalty to their defensive strength and penalty to their evade/parry/block chances. The only roleplaying verbs available to a webbed character are SWAY and WHEEZE; however, SWAY is unavailable to a character that is not standing. Webbed conditions are caused by a variety of mechanisms including Web (118), and spider creature maneuvers.
Additionally, some professions can gain access to special verbs and abilities to aid them while webbed:
Creatures That Web
(Via spell or otherwise)