This is typical of any framing lumber including rough sawn if fact its really different from one to the other much more so than standard s4s material.

You can either use a power planer to make them the same on top or shim up the lower ones. Using strips on top wont work all that well. J.

I agree with John: shim the short ones from below, where they rest on the beam. If they're really 1/2" off, then it's more "chunk of wood" than shim, but large shim/small shim it doesn't matter.

To lessen the difference, can you put the shorter joists on the beginning of the beam, and the taller ones on the part of the beam that slopes down?

If you bought your joist material at the same time/same place, there is no way you'd have a 1/2-5/8" differential amongst them. Sounds like your problem started with the posts/beams. It always helps if you start with a good foundation, as problems just multiply as you move up. That said, you can shim up the individual joists, and make it good. We just had a thread about a similar problem here at the gardenweb. Check it out for some pointers on fixing bad joistage...see the link below.
I hope you build a good railing for your walkway. Post some pics

steve

Here is a link that might be useful: fixing bad joistage

Thanks Steve and the Weedster, Good to see youall. J.

Brooklyn, you're right. I decided to add the walkway after I bought the other joist boards. I'll look at your link, thanks!
Weedster, I did move the taller joists to that side. But the 1/4" difference in the joists coupled with the difference in beams (It's a 24' long run and I split 2 beams over a post) has me in this little pickle.

I was actually contemplating notching the other higher joists underneath to split the difference but they have 3" ss annular ring nails toed through them into the top of the beam and those nails are not "quitters". Would it be better to shim up the beam instead? Or ripping one long shim out of some left over 4x12 to attach to the end in question? Since it's elevated, I'll probably stare at shims under the beams and point them out in disgust to everyone that comes over. Thanks for your advice guys!