Your spider is one of the many orb weaving spiders that are so active at this time of the year. Considered harmless to all but the insects that they catch, most would label them as beneficial and even beautiful.

They hide out during the day, and create a brand new web every evening.

I have them in my garden too, and really enjoy them. They are very active at this time of year, and I walk carefully down narrow paths because they spin those enormous webs across them, just at head level. I agree with rhizo -- as far as I know, they are harmful only to the bugs they trap in their webs. The webs are beautiful in the early morning after a heavy fall dew, when the sun catches the droplets of water and makes a lacy pattern out of the web. Don't worry, but look where you're going unless you want a spider riding on your hat.

Or on your nose, lol!