Filling ISP login form with a C# application

I have an ISP where I have to log in to the CityLan (100mbit to Fiber) before I get access to the Internet and I figured I might write an app to do it automatically instead of having to open a browser and do it that way.

My question is what the best way to do this may be. I suppose I'm a semi-novice, haven't developed for quite a while but should pick up on it rather fast (I still have my main C# book). The login-page in question is: http://login.hitnet.nu/axs-login.do?method=showLogin and I believe the login is javabased (from what I could see in the source). I suppose I need the app to fill out the input boxes. I have no idea how to look for them programmatically (and what kind of network code is needed to download the page or if I even need to do that). Perhaps there's a simpler way?