`` When I open some sites -LRB- e.g. Coursera -RRB- on Chrome , the page displays '' `` Ads by HQ-Quality '' '' in the upper right . Curiously , not all pages but some of them only display ads . What can I do to remove it ? ''
When I input site plus the domain , some pages are not seen , Google says it is due to the robots.txt . But why ?