Hey here's the scoop on the "Save for web" versus "Save as" question. I believe that ChrisH is right, most of my successful uploads to a.net I have simply saved using the "save as.." command. However, I have successfully uploaded using the "save for web" command as well and here's when it comes in handy: I shoot RAW files and after coming out of Camera Raw, I end up with a file width of about 1500 pix. After I do some minor tweeking, I resize the file to 1200 pix and then sharpen. After saving, the image is usually smack dab between 950kb and 1mb at the highest quality (12) jpeg setting. Occasionally, the file size will exceed 1mb.
This is where "Save for web.." can come in handy: after choosing save for web in photoshop CS2, there is a small triangle button in the top right corner of the frame. One of the options there is to specify what file size you want the "Save for web.." command to output for the final saved file. If you specify about 990kb, photoshop will find the best quality setting to achieve your specified file size. This usually results in a setting of between 98% and 99% quality setting versus the full 100% setting.
Your other option if your file size exceeds 1mb is to do multiple un-do's. Un-do your sharpening, un-do your image sizing, resize at a smaller image setting, re-sharpen and resave. That's five steps versus two using the "save for web.." command. To re-empasize, this is assuming your file is just over 1mb. If your file size is way over the 1mb limit, your only option is to resize and resave the file using the "save as command" because if you don't, using the "save for web.." command will overly compress your image.
Again, I think "save as.." is your best bet, but using "save for web.." can also work if you file size is just barely breaking the 1mb file limit for a.net uploading.