It all depends on your plan. Here's a can of worms....
IF YOU HAVE: America's Choice. Then you have to pay $5/month for mobile web access and it will use your airtime during PEAK hours.
IF YOU HAVE: Nationwide. Then mobile web access is included but only on a "pay as you go"** basis. $1.99/mb used while browsing.
**On either of the plans if you have a $15 feature for VCast Vpak then web browsing is unlimited and you don't have to worry about it.
On myspace it says it's free because MYSPACE doesn't charge you to access the site from your phone. VZW will.
But give us some details about your plan and what you're paying for and we can give you an exact answer.