Fixing broken pages for power users

If inspecting the revision History of a page does not do the trick, this is an alternative you can try.

Let us suppose that the broken page is called Mod:XMLerror (as here)
Try backing it up via this utility as described above. The backup appears to work even if the page is broken (although not all errors have been tested for)
This will fill the browser with code; you need to view source, copy the contents into (e.g.) Wordpad, and save as a file. Let us say you choose to name the file reload.xml.
This file looks like (in part)

<title>Mod:XMLerror</title>
    <id>40812</id>
    <revision>
      <id>156833</id>
      <timestamp>2011-02-24T20:55:08Z</timestamp>
      <contributor>
        <username>Rzepa</username>
        <id>1</id>
      </contributor>
      <text xml:space="preserve">= XML error =
[[Image:Molecule_1_(Jmol_Sample).gif|thumb|left|100px|Molecule 1<br clear="all" />
<jmol>
<jmolAppletButton>
<uploadedFileContents>pentahelicene.mol</uploadedFileContents>
<text>Molecule 1</text
</jmolAppletButton
</jmol>]]</text>
  </revision>

You have to identify the error and manually correct it using Wordpad. In the below, the changes are listed below
1. Change <title>Mod:XMLerror</title> to <title>Mod:XMLerror1</title> (in other words, rename the project page)
2. Correct the error. In other words, change </jmolAppletButton to </jmolAppletButton>
3. Save the modified file and go to Import and upload the newly corrected version of your report. It should be invoked Mod:XMLerror1

Caveat Emptor. Errors by their very nature are tricky things. Some errors might defy the above procedure, but since it is not easily possible to reproduce errors at will at all times, it is difficult to fully test the procedure out beforehand for all possible errors!