Christmas Card for a Building Society

It comes down to… if there are 2000 lines of code on a Html page. if I use 30 of them is that copyright, plagarism or whatever you wish to call it. I use someone elses style sheet and rename all the styles and incorporate it into my design.

Where do you draw the line.

As a matter of interest I think that you can use 5 seconds of audio from an existing astists release before it becomes copyright!