I've just tessellated the bottom to 512 surfaces, now some of the surfaces dont have a white edge to them, why would that be?

Those are faces that werent tesselated. and BTW, press f4 to get rid of those "white lines" they are the outlines of edges, and they help.

how should i tesselate them now then?

Go into face/poly selection mode, select all the non-tesselated faces, and click tesselate until the "white-lines" on them look like the other tesselated ones.

the thing is when i select all the faces, i read 512 in total though>

Select all faces of your whole map/model? It doesnt really matter if some aren't tesselated anyway, unless you plan to use the other face for modeling.

ok ill carry on regardless,

I mean the "untesselated" faces may not have the white edge like i said b4 but u can still select individual faces from them . If that made sense....

Also if ure any good at tool errors please see my

TOOL STRUCTURE PROBLEM a bit further down!

Thanks , well ill give it a go if tool throws any errors up ill be sure to post!

I doubt youd get an error. If you do, its totally un-related.

No errors here

just go into edge mode and create a new edge where the line is. or you can convert the model to editable patch then back to editable mesh/poly. that will make sure all polys are divided into triangles.

in poly mode (red square), you select faces bound by visable edges. If you make all edges visable, you can click any face as a poly. You can also select single faces in Face (red triangle) mode
In edge mode (red outline triangle), you can make edges visable/invisable