How to make web site accessible which hosted in different gateway

We have hosted web site (IIS) in our local network.

This machine IP 192.168.5.25 and default gateway is 192.168.5.1

Now I want to access this web site from machine in different gateway.

That machine IP 192.168.6.30 and default gateway is 192.168.6.1

Both networks are connected using VPN and we can ping and access from 
both sides. But cannot access web site. What I have to do in order to access
this web site.