Here Elsevier say that authors may put preprints on arXiv, and that they may put accepted versions on arXiv. They define a preprint as something that has not been peer reviewed, nor had any other value added to it by the publisher.
They do not seem to say anything explicitly about posting intermediate versions, that is, versions that have been revised as part of the peer review process but have not yet been accepted.
I would like to post to arXiv a significantly revised version of a paper that has been accepted subject to minor revisions. The Elsevier website does not seem to address this case. Is posting the paper acceptable? Is it common practice?
The rationale for wishing to post this version is to be able to refer to new results it contains. But I can understand a journal not wanting such intermediate versions to be posted. Their peer review process has added value, but until the paper is accepted it's hard to give the journal credit.