Safari

  1. Menu → Settings
  2. Go to Extensions
    • Remove unknown extensions
  3. Reset Homepage & Search

Chrome

  1. Chrome Menu → Settings → Extensions
    • Remove unknown items
  2. Reset search engine:
    • Settings → Search Engine
    • Ensure Google is selected
  3. Reset startup pages

Firefox

  1. Menu → Add-ons and Themes → Extensions
    • Remove unknown items
  2. Reset search preferences