[AlanHK]

I imported a KF8 into Sigil using the KindleImport plugin to make an epub2.

This looked OK, but when I started checking out styles, clicking on any style in the code window to "Go to link or style" gave the message
"No CSS style named ".Center" found, or stylesheet not linked".

But the style clearly was being applied in the preview. The inspector showed the relevant line in the style file.
Epubcheck showed no errors.

Eventually I looked at the Book Browser list and clicked "Link stylesheets", to see no stylesheet was linked. Though it was, and the styles were working.

Used the link popup to add the stylesheet and saw that the new link was

<link href="../Styles/style.css" type="text/css" rel="stylesheet"/>

the original link was

<link rel="stylesheet" href="../Styles/style.css"/>

i.e., the original link had no type="text/css".

So either Sigil should recognise this as a valid style link, or add the "type" code on opening or with "mend code".