This is an HTML 5 feature and is not natively supported by UFT. You can't do any checkpoints on it because it is not persistent and goes away immediately upon losing focus. However, there is a way around it:
1. Open the object repository and highlight Test Objects in the left pane.
2. Click the Define New Test Object icon.
3. Set the following properties:
Name: Whatever you want. For this example, we'll call it Validator
4. Click Add.
5. Click the Validator object in the object tree.
6. Change the Ordinal Identifier to Type:Index, Value:0
7. With the Validator page still highlighted, click the Define New Test Object icon again.
8. Set the following properties (Delete any other properties):
Name: Whatever you want. For this example, we'll call it Validation
html tag: DIV
html id: contentContainer
9. Click Add.
10. In your test, do whatever causes the validation message to appear.
11. Use the following code to grab the text of the validation message:
strMessage = Page(''Validator'').WebElement(''Validation'').GetROProperty(''innertext'')
Now you can validate that strMessage contains the text you expect.