Eclipse doesn't like jQuery and each time I begin from a new install, I need to configure it to ignore validation errors on jQuery. I hate that little red x.
Steps To Remove This Little Red X
Select your project in the Package Explorer (or however you do it)
Click Edit... on the right
Click Add... in the exclusions
Browse to the jQuery file. If you use a pattern, it may exclude other files so use your head and exclude only what you intend to.