According to Brent in the Search Engine Roundtable Forums, Microsoft adCenter is now providing more information into why they are rejecting keywords.
Some of the reasons are:
- Too much ad text (keyword parameter use exceeds character limits)
- Landing page content not relevant
- Website contains forbidden content - Content guidelines
- Incorrect ad format - Style guidelines
- Not enough ad text - The combination of ad title and ad text is less than 6 words
Forum discussion continues at Search Engine Roundtable Forums.