Read the instructions that you get in the popup when you download the
theme. It explains it.
jquery.mobile.theme.css
is a pasted-together file combining all of:
- default theme
- default icons CSS
- "structure" (CSS related to layout)
It has everything you need, if you are NOT going to use your own theme.
If you use your own theme, do NOT use the default file that
contains all 3 parts!
All of the parts can be downloaded separately. You get the theme
from theme roller. You get the other parts from the download site.
There are also multiple options with icons. It depends on whether
you intend to use SVG icons, PNG icons, both (SVG with PNG for old
browsers that don't support SVG) and whether or not you want to
use inline images (encoded right in the CSS) or external images
(links). The standard way is inline SVG with external PNG fallback.