# Why selecting text in my notebook become abnormal?

Selecting text in one of my Notebooks becomes abnormal.

Here is the unselected text:

and here is the partly selected text:

When the text being selected, it should be like this:

What is wrong with this Notebook? my other Notebook is OK!

Here is my abnormal Notebook.

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Behavior confirmed in version 7, but I don't know what is causing it. –  Mr.Wizard Jul 19 '13 at 1:41
Similar behavior in V9.0.1 on OS X 10.5.8 –  m_goldberg Jul 19 '13 at 2:07
If I do a Select All on the downloaded notebook, copy the selection, and paste it into a new notebook, highlighting works as expected in the new notebook. Perhaps you can do the same to recover control over your work. –  m_goldberg Jul 19 '13 at 2:28
This question appears to be off-topic because it is too localized; i.e, it applies only to local situation and needs of its poster. –  m_goldberg Jul 19 '13 at 2:29
@m_goldberg You may have noticed that "too localized" is no longer a listed reason for closing. ;-) Anyway, in this case I disagree as it's a curious problem until the solution is revealed, and it could potentially affect anyone who comes across such a Notebook. –  Mr.Wizard Jul 19 '13 at 6:18

Your notebook has an option set, ShowSelection -> False, which is causing the problem. Use the Format > Option Inspector... and search for ShowSelection; then click the checkbox to set it to True. Or execute SetOptions[EvaluationNotebook[], ShowSelection -> True] in the notebook.