According to your screenshots, QuickLook appears to be working. You keep asking for screenshots. OK. Here you go:

The selected file is the index file from one of my websites. You can see the Finder preview thumbnail in the right hand pane. I have pressed the space bar to display the full QuickLook preview image in a separate window.
On the right, in the Finder Preview pane, is a QuickLook preview of the document. When it does the thumbnail preview, it doesn't appear to include CSS style sheets. I guess it does that for performance reasons, which makes sense. The full preview includes the style sheets.
Could you include a screenshot of your own that shows the feature not working? So far, the only screenshot you have provided is on that shows it is working.
And can you PLEASE clarify what you mean by this 'app "Quick look"'? Do you have an app called "Quick Look" in your applications folder? If so, that is what is causing your problem. Drag it to the Trash and empty.