I want to add new pages to a website without being have to recompile the whole site and copy the new dll to the bin folder.
I just want to upload the aspx files + the cs files.
Right now, when I try to do it the page won't load.
If you are working with a Web Application Project, you have to compile and copy the dll and aspx files.
In your case you could also use a Web Site project. ASP.NET will compile your code while it's being accessed so you can only deploy new aspx and cs files.
Here you can find an overview of the differences between Web Application Project and Web Site Project and also a few hints on when to choose which.