When you try to edit Font Size property in your css file using CSS Properties View, the source file is not edited properly and the Error message appears( An error occurred while setting the value).

Detailed testcase:
1. Create css file.
2. input the next css class - .classA

3. open CSS Properties View
4. in series delete all digits in "Font Size" field
5. ASSERT: error message appears
6. try to input fractional number again
7.ASSERT: font-size attribute contains only dot instead number