In my OpenGL 2D application, i have a number of objects on screen and their coordinate values are based on my systems resolution. How do i optimize their positions for all resolutions? I mean, i want them to be independent of any particular screen size, so that they stay at proportionate distances on any screen, as designed during development.Are there any functions which can take care of the matter?

Just don't pass actual screen resolution to glOrtho to setup the coordinate system, but instead use the fixed design resolution you have.