Mesh created with connected vertices don't create correct mesh I started with a simple plane mesh and then continued working with by creating new vertices by selecting the edges and then subdivide them. Then I connected two vertices with F button to create a new mesh and continued working like this, but it seems there are problems in model, because all visibile meshes are not real meshes and I can't select them! The normals show those who are correct.

I searched for info about this and found that a manifold thing could be the problem, but I'm not sure how to make this model correct again?

To create meshes with new vertices on edges and also create them with CTRL button and a mouse click and then connect them with another edge or vertex, is this not a recomended way of working or how can I avoid getting this problem in the future?

Preciate some help to be able to continue with my model.
Yes; I would highly advise against modeling in this way. It would be much better to use extrude operations (E key) to create your mesh.

If you wish to continue with your current mesh, two ways I would recommend trying to fix it is by first removing any doubles (Spacebar > Search "Remove Doubles"), and then recalculating the normals in the 3D View Tools menu:



If you can attach a Blend file, I could take a look at your mesh and see what else may be able to be fixed, but I would honestly recommend starting from scratch on this one and modeling with better practices.

EDIT:

Here is an example of how you might start building a mesh with extrusion and loop tools, although for a car, I would highly recommend using Background Images of your car and start working your way around that. Here is an excellent resource to get you started in that workflow: http://darkscarab.com/view/43