DPS has nothing to do with eBooks or ePUBs.
What are you trying to do? If you are using Indesign simply use the character panel to set the text size.
dont worry i think our Developers must up creating our eBook publications, they will need to sit and go through fixign the issues..... my 2nd Question is.. i have and eBook which i used AdobeDE2.0 to download my eBook how do i get my eBook to work on another device
Moved to ADE forum.
If the device is a dedicated eBook reader compatible with ADE, plug the device in and it should show up in ADE.
You need to register the device (ADE should ask you to automatically), and then ADE will let you copythe book.
There are quite a few bugs in ADE2.0 that prevent it working with certain devices. In that case, install and use ADE1.7.2 intead.
Version 1.7.2, it is a little difficult to find, available on Adobe site for Windows and for Mac.
The forum software is sometimes corrupting the link above. There shouldn't be a blank in 'editio ns.html'. The following redirects to the same page: http://tinyurl.com/diged172
If it is something like a tablet, you need to install appropriate ebook reading software compatible with ADE: I suggest the Bluefire app.
The copy the epub to the device and open with Bluefire.
If it's an Apple device, you need to copy indirectly using something like Dropbox, iTunes or emailing yourself.
Don't specify font size in pixels (px), use points (pt), ems (em) or percent (%) instead. Better yet don't specify the font size at all for your body font.