I have finally discovered the solution to my query after much investigation. Surprisingly, the issue lies not in the property 'mso-number-format
', but rather in how Visual Studio 2008 interprets it. This specific property is considered non-standard, hence the validation error is warranted. Nevertheless, this should not hinder the project from compiling successfully.
Typically, Visual Studio 2008 is programmed to consider HTML and CSS errors as mere warnings by default. Yet, due to a potential installation glitch, these errors may be mistakenly flagged as true errors instead. The resolution lies within: Tools | Options | Text Editor | HTML | Validation. Make sure that under Target, both checkboxes for Show errors and as warnings (HTML, CSS) are ticked. In my situation, they were already checked, yet errors persisted as errors rather than warnings. I unselected the boxes, clicked OK, then returned to reselect them before confirming with another click on OK. Voila! Problem solved.