[kevinklee2003]

Question: If Ksp for most substances is so negative,then why we don't see solids normally in solution?

So for most substances, the solubility of a substance lies far to the left, being very negative.
This means that for a reaction like:

AB(s) -><----- A+(aq) +  B-(aq)

The equilibrium favors the solid much more than the dissolved form with the ions.

If you add enough ions to make the reaction quotient (Q) > Ksp, then the reaction shifts towards the products and you get precipitate (common ion effect).

But if the reaction already lies so far to the left, where the heck is the solid from before we added more ions?  Is it dissolved but not dissociated? What's going on here?

[Babcock_Hall]

For starters, K_sp is never a negative number.  In addition I would question your use of "most."  Many substances, such as alkali metal chlorides and many nitrates, are quite soluble.