Mobile/handheld stylesheet design by default for clients?

Hi,

Just like to know what recent trends are in developing mobile/handheld stylesheets for client websites:

  • Do you design them in by default (without clients asking)?
  • Encourage client to consider mobile/handheld stylesheet from the beginning?
  • Wait till client asks?

Also, what is reasonable to charge to retrofit a mobile/handheld stylesheet to an existing website?

Thanks for your input,
VWD