hi,
i was going to try out some of the shaders for download on this site but i can't seem to use them 
I assume you just save the preset file and then use it like any other shader. Except it doesn't seem to work
I tried to open a node via the rendertree as well as drag and drop from the browser view but still nothing 
am i doing something wrong?
first, open the shader properties form the object you want to use the shader and then load a shader preset (click on the load buttom in the right corner in the propertie sheet). you must have the right shader, the presets only work in this, eg. a lambert shader preset only work in lambert shader, the same in photon shader.
look at the discription when you download.