"A journal editor reveals the top reasons so many manuscripts don’t make it to the peer review process:
1. It fails the technical screening.
2. It does not fall within the Aims and Scope.
3. It's incomplete.
4. The procedures and/or analysis of the data is seen to be defective.
5. The conclusions cannot be justified on the basis of the rest of the paper.
6. It's is simply a small extension of a different paper, often from the same authors.
7. It's incomprehensible.
8. It's boring."
Details about each item, see here: http://www.elsevier.com/connect/8-reasons-i-rejected-your-article