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?