Eclipse Force.com IDE – Javascript Syntax Highlighting in Kepler

Open Eclipse
View the ‘Help’ menu
Select ‘Install New Software…’

Enter a Name. Anything will do.
Enter the Location: http://download.eclipse.org/webtools/updates
Click ‘Add…’
Click ‘OK’

Check ‘Eclipse Web Developer Tools’
Check ‘JavaScript Developer Tools’
Click ‘Next >’
Follow the prompts to install.

http://download.eclipse.org/webtools/updates