I'm trying to tie together some websites into a single one I can use as a portfolio to send potential employers.

The old sites positioned everything to fixed sizes and I'm converting it over to percentages or em measurements. At the same time, I set a minimum width of like 600px, and it's responsive at sizes above that but if you shrink the browser down to an inch or two it'll shrink to a minimum of 600px.

So I'm wondering how many pixels wide is the smallest android/iOS smartphone? Would 600px still go beyond it's screen size? Should I make it 400px or something else minimum?

.Also I'm using a mobile doctype for the site rather than xhtml transitional, both validate so I dunno what the difference is between the two....

Any advice?