ok…another information:
when i turn on blendig at the rotating teapot then i got the same dark lines
at the teapot triangles/quads
it seems that the problem has only to do with vertex buffer thing itself
…when disabeling texture and work only with colors the line problem stays!
i use the actual release of jogl libs
What happens when you turn off anti-aliasing?
hm, when i download the images, i see there is no anti-aliasing (Opera scales them very smoothly…)
i got it!
on some pc the lines were not visible.
i tested with setting and found…all systems that got
nvidia graphics and setting: “Anti Alaising…setting from software”
produces the lines!!!
(after overide the software setting in the driver control to 2xAA all graphic were fine)
so i need to set/activate AA in the application to
prevent such graphic errors
(hope i find a simple explanaition for it)
thanks to all 
Another way to attack the problem might be to render a complete mesh in one operation rather than individual triangles.
[quote]Another way to attack the problem might be to render a complete mesh in one operation rather than individual triangles.
[/quote]
i was also thinking about this,but the "teapot"object example that is included
is rendered in one piece…and with blending its same…
i only need something like this:
gl.glEnable(GL.GL_AntiAlaising,AA);?!?!?!
but i can find anything here via search