User-Agent: Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.6; en-US; rv:1.9.2.9) Gecko/20100824 Firefox/3.6.9 Build Identifier: Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.6; en-US; rv:1.9.2.9) Gecko/20100824 Firefox/3.6.9 See the attached URL for a working example of the problem which appeared in Firefox 3.6.9. If a <pre> has contentEditable=true, deleting the first character on a line will bring that line up to the previous line. Similarly, trying to enter a character with the caret at the beginning of a blank line will actually add the character to the next line. The demo url is the best explanation of this. Reproducible: Always Steps to Reproduce: 1. Click inside a contentEditable div 2. Delete the first character of any line Or 3. Add a character at the beginning of a blank line. Actual Results: Deleting the first character of a line moves the rest of the line to the end of the previous line. Adding a character to the beginning of a blank line actually adds it to the beginning of the next line. Expected Results: Characters should be inserted and deleted without changing surrounding lines.

Seems to be WFM on Trunk on WinXP (Mozilla/5.0 (Windows NT 5.1; rv:2.0b6pre) Gecko/20100913 Firefox/4.0b6pre ID:20100913041656).

This has been fixed on trunk by some of the patches that I landed as part of the work in bug 240933.