I'm looking for possible alternatives to Dreamweaver for editing HTML documents -- in particular, open source alternatives.

For me, an "alternative" is an HTML editor that at least approximates Dreamweaver's ability to display source data and a formatted (WYSIWYG) display, keep them in synch, and let the user edit either one. (It should have a reasonable set of features for formatting, validation, auto-completion, etc, but that is almost a goes-without-saying item.)

So far I haven't found a single editor that offers synched, editable source and WYSIWYG displays. I'm puzzled: has the open source community simply neglected to produce any offering in this area? Or am I missing something?