Unable to display this Web Part. To troubleshoot the problem, open this Web page … & Error: Reference to undefined entity 'nbsp'

Question

I created a page in SharePoint Designer 2007 that use a SharePoint Library. I used the method of 'generating XSLT' from this page - How to customize the header titles of the List Views web part without renaming the List?

At first, the page did work as expected. However, after a long while, the page fail to work and display the following message (at the Internet Explorer):

Unable to display this Web Part. To troubleshoot the problem, open this Web page in a Windows SharePoint Services-compatible HTML editor such as Microsoft Office SharePoint Designer. If the problem persists, contact your Web server administrator.

So, I went to open the page in the SharePoint designer and notice the following error:

This Web Part does not have a valid XSLT stylesheet: Error: Reference to undefined entity 'nbsp'.

So, my question is:

[A] What are the causes that result in such error message (even though that it is working in the first place)?

[B] What are the solution or workaround to solve and prevent such error message from occurring again?

Answer 1

At last I found the problem.

Simply change the &nbsp to &#160 for the XSLT code will solve this problem.

Answer 2

I think you have made a typo and included nbsp somewhere in your XSLT, instead of &nbsp. Correcting that should fix the issue.

&nbsp is an entity used to declare non-breaking space in HTML. I suggest you do a search for nbsp and change it to &nbsp in your XSLT.