I have made a custom search portal for a sharepoint library. As instructed in a different topic here I have selected the stylesheet in the Settings of this site. But it seems this also applies to all top-level sites and document-library views. How do I apply a stylesheet to a single site?
Put a Content Editor WebPart on te page with a LINK to a CSS file.
If it's not a WebPart page you have to go the more technical route:
document.head in the MasterPage itself; but you need to check the URL for execution on the correct page
Easy to attach using the SPEditor Chrome Extension: