Sorry, not enough info - spiders do make cobwebs over hedges, etc., at this time of year, quite normal - a very thick amount of cobweb sometimes indicates tent caterpillars of some kind, but they're usually in trees - these should be cut out in winter, once you've worked out what they are - one of the caterpillars (a moth, can't remember its name) has brown furry spines which cause breathing difficulties in some people, and contact dermatitis. Can't tell if its any other problem - you haven't said what plant is affected.

If it's extremely finely woven, like a nylon stocking, it might be a severe infestation of mites. Sometimes you can see the little yellow, rusty, or greenish mites crawling around on the webbing, if you look really close. They are as small as the periods on the page, and are sometimes easier to see if knocked onto a piece of paper.