For photographing spiderwebs, I always use live view on 10x magnification and manual focusing.
Play with getting the
light to reflect off the web as in the following image, but you will notice in this image that the web disappears from sight where it is in shadow, on the right hand side! This requires looking at the web from all manner of angles, until you get those magic sparkles to pop. Try and get a neutral background to set it off from too, if at all possible, which may mean coming back at a different time of the day to achieve this, as I had to do with this shot. You could always cheat and bounce the
light from a flash off the web to achieve the same sort of look!
https://photos.smugmug.com/photos/i-...L3xB9kT-XL.jpg
Golden Orb Weavers spiderwebs show up really well against a nice neutral background.
https://photos.smugmug.com/photos/i-...Tc54JxT-XL.jpg
Another web, pretty messy this time and occupied by a tiny spider, but the web is shown off fairly well because of the darker background it's set against.
https://photos.smugmug.com/photos/i-...Tjv87Qg-XL.jpg
Another messy web, this time in full midday sunlight and set against some old rusted out machinery.
https://photos.smugmug.com/photos/i-...ddmxqLZ-XL.jpg
All of these were achieved on a
tripod and with live view at 10x magnification, to make sure that my manual focus was correct. Hope that helps you a little.