The cobweb, because it is easily damaged, signifies indecision, perhaps an idea that has not quite crystallized yet.
On a purely practical level the cobweb symbolizes unused talents and potential which has been allowed to go stale.
If there is no spider in the web, it indicates calm days and happy times ahead. If you see a web being spun, you’re in soon for some criticism.
The evidence of timely entrapment, and a warning to beware; see “spider”