How to reproduce it :

• In chrome with english language, open link directory panel
• click on the arrow of the "New link" button of the ribbon
• click on the "To a page of site" button
• The focus of the cursor is already on the first field,
• click on the button juxtaposed to select a page
• As soon as the focus has quit the input, the field take up the error style

That create a blink effect while the window to select the page is opened.