Shared components used by Firefox and other Mozilla software, including handling of Web content; Gecko, HTML, CSS, layout, DOM, scripts, images, networking, etc. Issues with web page layout probably go here, while Firefox user interface issues belong in the Firefox product. (More info)
Right now AbortPar's location isn't very helpful in the spew since it replaces a whole block. For speedier debugging we should make it more precise, perhaps make it remember which MIR it replaced and what its location was.