Firefox:
to adjust dpi go to about:config and search for:
layout.css.devPixelsPerPx
change value accordingly: laptop is 1.33
Chrome, tips and tricks here (useful for firefox too):
http://mashable.com/2010/09/09/chrome-tips-tricks-shortcuts/
http://lifehacker.com/#!5045904/the-power-users-guide-to-google-chrome