Pre-Algebra · Superchallenge problem

Each blank in $1\;\_\;2\;\_\;3\;\_\;4\;\_\;5\;\_\;6\;\_\;7\;\_\;8\;\_\;9\;\_\;10$ is filled with a $+$ sign or a $-$ sign, and the result is worked out. How many different results are possible?