Grading scores from 0.0 to 1.0
Yes, your code is correct, although I would recommend adding comments, and following the style guidelines of PEP8. Here are a few tips I have. 


You should specify what type of error you want to except. If you just type except:, other errors could go un-noticed. 
Typing exit() really isn't needed here. The program will terminate either way.
You don't need to put parentheses around conditionals in if statements. 
It seems also that you're using Python2, so no parentheses are needed for print.
You could make this into a function that returns the grade.


Here's my re-factored version of the code.

def return_grade(user_input):
    """
    Return the user's grade based on the following table.
    Score  | Grade
    -------+------
    &gt;= 0.9 | A
    &gt;= 0.8 | B
    &gt;= 0.7 | C
    &gt;= 0.6 | D
    &lt; 0.6 | F
    """
    try:
        user_score = float(user_input)
        if user_score &gt; 1.0:
            return "Please enter a number between 0.0 and 1.0"

        elif user_score &gt;= 0.9:
            return "Grade: A"

        elif user_score &gt;= 0.8:
            return "Grade: B"

        elif user_score &gt;= 0.7:
            return "Grade: C"

        elif user_score &gt;= 0.6:
            return "Grade: D"

        elif user_score &lt; 0.6 and user_score &gt;= 0.0:
            return "Grade F"
    except ValueError:
        print("Please enter a number.")


print return_grade(raw_input("Enter a number between 0.0 and 1.0"))