If you have trouble getting to the firmware recovery page when going from DD-WRT back to d-link firmware i have a solution.
Hardware: DIR-810L rev b
Problem: After doing 30/30/30 reset, can't connect to the firmware recovery page at 192.168.0.1 in any browser, router does not respond on ping at 192.168.0.1
Solution: Stock DD-WRT gives the router the ip: 192.168.1.1. Change it to 192.168.0.1 and reboot the router. Now perform the 30/30/30 reset (or do the fast reset ; see below). The firmware recovery page should be available at 192.168.0.1
Fast reset: when the router is turned on pull the power plug. Power plug still out press and hold down the reset button and plug in the power cable again. Release the reset button when the POWER LED starts flashing orange.