I'm building my first mobile site (mobile only, not responsive), I just have some basic questions I was hoping someone could help me with or point me in the right direction to get started. Thanks in advance.

1. Is it safe to assume that javascript is alway on, or should I code fallbacks incase js is off?

2. With CSS properties, do I need to worry about browser prefixes? For example, would I need to do this:
Code CSS:
background: -webkit-linear-gradient(top, #2F2727, #1a82f7);
background: -moz-linear-gradient(top, #2F2727, #1a82f7);

or could I just the CSS3 standard:

Code CSS:
background: linear-gradient(black, white);

3. I am building nested navigation almost identical to this: http://ui-cloud.com/res/designmoo/Ac.../accordion.jpg
except the sub nav will slide up. Should I build this the same way I would for a desktop browser, maybe like a jQuery accordion? Or is there just a better way to do this with iPhone/mobile? Are CSS transitions better to use on mobile?