View differences between two changesets on one file

hg diff -r <first_revision_number>:<other_revision_number> filename

that will do it

e.g hg diff -r 0:1 default.aspx

hope it helps

If you know the revision numbers, then what PaulStack said is correct.

If you explicitly want to know the difference between the current tip of the branch, and it's previous, you can use shortcuts. Of course, if the file hasn't changed, the diff won't show anything useful.

hg diff -r -1:. filename

The -1 says previous changeset on this branch. the '.' means the current changeset. You can use -2, -3 etc, but once you hit a merge point, it gets a little more interesting. (reference: http://hgtip.com/tips/beginner/2009-10-05-shortcuts-for-specifying-revisions/)

If what you want is the outstanding changes in your workspace, then it's merely hg diff filename.

A few useful places for HG newbies is http://hgtip.com.

The HG definitive guide at http://hgbook.red-bean.com/.

A stackoverflow like site that's more HG specific is the Kiln support site. http://kiln.stackexchange.com. Kiln is built on top of HG, and uses a modified TortoiseHG client, so most of the questions and answers there are informative. They will also answer questions even if you aren't a user.