Participating in a hackathon as a beginner is a great way to learn and apply your skills. Here are some simple project ideas suitable for beginners:

1. Personal Blog: Create a blog website where users can write, edit, and publish their articles. You can use HTML, CSS, and a basic server framework like Flask or Express.js.

2. Task Tracker: Build a web application that allows users to add, update, and remove tasks. You can use HTML, CSS, and JavaScript, along with a simple database or localStorage for data storage.

3. Calculator: Develop a web-based calculator that performs basic arithmetic operations. It's a great project to practice your HTML, CSS, and JavaScript skills.

4. To-Do List with Notifications: Create a to-do list app that not only manages tasks but also sends email or browser notifications for upcoming tasks. You'll need to integrate an email service and use JavaScript for notifications.

5. Weather App: Build a weather app that retrieves weather data from a public API and displays it to users. Users can enter their location or allow the app to detect it automatically.

6. Currency Converter: Create a currency conversion tool that takes an amount in one currency and converts it to another. You can use a currency exchange rate API for this.

7. Trivia Quiz Game: Design a trivia quiz game with multiple-choice questions. You can use HTML, CSS, and JavaScript for the front end and a simple JSON file to store questions and answers.

8. Quote Generator: Build a web app that generates random inspirational quotes. You can store a list of quotes in an array and use JavaScript to display them randomly.

9. Countdown Timer: Develop a countdown timer that counts down to a specific date or time. Users can input the date and time, and the timer will update in real-time.

10. Recipe Finder: Create a recipe app that allows users to search for recipes based on ingredients they have. You can use a recipe API to fetch data.

11. Simple Chat Application: Build a real-time chat application that allows users to join chat rooms and send messages. Use technologies like Socket.io or Firebase for real-time updates.

12. Basic E-commerce Store: Create a simple online store where users can browse and purchase products. Use mock data for products and implement a basic shopping cart.

13. Guestbook: Develop a guestbook where users can leave comments or messages. You can use HTML and JavaScript to build a simple form that appends messages to a list.

14. Tip Calculator: Build a tip calculator app that calculates the tip amount and total bill for a restaurant meal. Users can input the bill amount and tip percentage.

15. Note-taking App: Create a basic note-taking app that allows users to add, edit, and delete notes. You can use HTML, CSS, and JavaScript to create the user interface.

16. Weather Dashboard: Build a dashboard that displays the weather forecast for a user's location along with other information like news and events.

17. Daily Journal: Create a digital journal where users can write daily entries, add images, and search past entries.

18. Flashcard Quiz App: Develop a flashcard app for learning new topics or languages. Users can create decks of flashcards and quiz themselves.

19. Movie Recommendation App: Build an app that recommends movies based on user preferences, such as genre, ratings, or actor/actress.

20. Task Scheduler: Create a task scheduling app that allows users to set reminders and notifications for important events or tasks.

Conclusion

These ideas are designed to be manageable for beginners while offering valuable learning experiences. Choose a project that interests you and aligns with your current skill level, and don't be afraid to seek out online tutorials and resources to help you along the way.