getting rid of annoying border edge.
 

I'm sure there must be a solution to this problem, which ive had a couple of times before. In the picture you can see i've got a border edge running along the side of my model. This stands out alot when smoothed and rendered, and 'sucks' in and distorts some of the surrounding geometry. I've gone all along it making sure that its not a merging verts problem. I had a similar line elsewhere on my model when i attached two objects together from which id deleted faces. The solution then was to run edge loops across it, but that doesnt work here either. Its come (Im sure) from how in some areas ive extruded faces, and in others ive switched to extruding edges. Has anyone got any ideas of what exactly the problem might be or any suggestions of how i could cure this?

Check the normals on both sides of the border edge and make sure they're facing the same way. This can also be caused if you have messed up geometry there - try to select one face and make sure there aren't actually two faces there (in the same place).
You might need to use cleanup but it usually doesn't get that far if you have good working habits.
Benny

cheers benny. reversing the normals worked for most of it. I dont realy understand how that would have come about in the first pace though.