NOT MALE DOMINATED. I am one of MANY females "working the web", and our numbers are increasing.
Math: That may depend on the college/program you choose. Courses/degrees in the internet field are still relatively new, so they can vary greatly. Check out a few colleges you think you could attend and see what degree they offer and what courses are required. At minimum, you can count on taking the math required under general ed. for an associates degree - maybe college algebra 2.
What programs you learn will again be dependent on the college - most of them pick one platform/web server combo and go with it. These are usually popular choices, so they'll be a good bet. But you can gain experience with other platforms/softwares by taking advantage of free/low cost hosting offers, or thru internships, volunteer work, or "side jobs".
Web Developing and Web Page Designing go hand in hand, and often the same person does both - at least at small- to mid-sized companies.
Web Page Designing is focused more o