A search engine trick by some seos is to manipulate the search bots by loading the page with keywords and phrases — but then hiding them from the viewer because they’re not relevant to the visitor. For example: using white text on a white background, or using text behind an image, or setting the font size to 0.
If your site is perceived to contain hidden links or text, it can be removed from Google’s index, and won’t show up in any search pages. Google evaluates web sites to see if they include hidden text or links, and look for any content not viewable by your visitors.
If your site does have hidden text or links, either remove them or, if they are relevant for your visitors, make them viewable.