I created a fillable form in Acrobat Pro 9 which is to be used for data collection on a website, and emailed once completed. When viewed in a PC based browser, the actual fields are obvious, and the "submit" button is in the upper right corner of the form/page. When the exact same form is viewed in a mac based browser, the "submit" button is missing, and there is no obvious way to send the form.
I think you are talking about a Acrobat form and and a FormsCentral form.
You might want to post on this forum instead : http://forums.adobe.com/community/acrobat/forms
One thing I can think of is that the filler needs to use Adobe Reader or Acrobat to fill out and submit the form. Is it possible that the filler on the mac is using Preview to view the form (which is the default for that OS I think)?