Welcome to the Ranch.
If I understand your question correctly
1) Your html file has two parameters called userID and password
2) You are trying to access the values for these parameters from your GWT code.
3) While attempting to do so, you end up with a NullPointerException
Is this correct?
If yes, please post the code where you are trying to access the values.
If no, please rephrase your question.
Also, please do take out time to go through
http://faq.javaranch.com/java/HowToAskQuestionsOnJavaRanch