It really depends on the market you're trying to address. I would assume that most phones sold in the developed markets in the last two years have browsers with

It really depends on the market you're trying to address. I would assume that most phones sold in the developed markets in the last two years have browsers with XHTML+CSS support. But, tons of low end phones are still sold the world over. They may support only WAP. We started with WAP on a project and quickly gave up.