linking kernel source?
 

I have the sybolic link /usr/src/linux . Is this used so when I compile programs that need the kernel source, they can easily find it? Does it make a difference if /usr/src/linux is linked to my 2.6 or my 2.4 kernel? If a program was compiled with the /usr/src/linux linked to my 2.6.0 kernel, can it cause problems if run with my 2.4 kernel?

Not really, most programs might not be linking to it, only in some cases lib's and drivers. Usually during the compile, it will tell you if it looked for the kernel header files, etc.

thank you:)