Router for load balance

We are using 2 ISPs currently in our company with individual router provided by each ISP, and I get both of these routers connected to the same switch, my question is how can I configure the individual router(i.e. a routing table) in order to ensure a more or less equally splitted traffic through these 2 routers?? In addition, I want to include a web server with the LAN. Thanks advance for any help.