This works for me...
(Just substitute the google, yahoo and bing links for your own)
(BTW: You can substitute iexplore with chrome to open them as tabs in chrome too)
Note: Ensure the specified browser is your default browser, else it will open the first in one browser and the rest in the second browser.
The ping line is just a timer to allow foe the browser to first load
@echo off
start iexplore
http://www.google.com" onclick="window.open(this.href);return false;
ping localhost -n 2 > nul
start
http://www.yahoo.com" onclick="window.open(this.href);return false;
start
http://www.bing.com" onclick="window.open(this.href);return false;