You didn't mention what frameworks you gonna use. If its just Javascript, jQuery, html, css than expect these questions:
1. What is closure and how it works?
2. What is prototype in Javascript?
3. How do you implement inheritance in Javascript?
4. Be familiar with arrays, algorithms, substring, sorting, etc
5. diff between div and span
6. css positioning
7. css selectors
8. what is symantic html?
9. What have you used in html 5?
10. have you done SCSS\SASS
11. what is sprite in css?
and so on