Here is the full list of all 16 wurdweb achievements.
Complete the Tutorial
Complete 10 puzzles in Tangle Mode
Complete 10 puzzles in Precise Mode
Complete 100 puzzles in Tangle Mode
Use hints 100 times
Complete 100 puzzles in Precise Mode
Use undo 100 times
Place 1,000 words
Complete 7 Daily Puzzles on different days
Place 4,000 words
Complete 4 Weekly Puzzles in different weeks
Place 10,000 words
Complete 6 Monthly Puzzles in different months
Complete a Daily Puzzle
Complete a Weekly Puzzle
Complete a Monthly Puzzle