Should I avoid javascript , jquery, flash, ajax, silverlight if i want to make my site cross platform compatible and screen reader compatible?

Question

Should I avoid JavaScript , jQuery, flash, Ajax, Silverlight if i want to make my site cross platform compatible (PC, iPHONE other mobiles, PDA) and Accessible(screen reader compatible)?

Should i only use xhtml css with server side language for wider accessibility?

and for PC pr MAC i made everything first for Firefox so for mobile which browser should i choose?

Answer 1

No, but offer them as progressive enhancements or provide graceful degradation.