procedure HandleStyleSheets(const Document: IDispatch);
var
  Doc: IHTMLDocument2;                      // document object
  StyleSheets: IHTMLStyleSheetsCollection;  // document's style sheets
  SheetIdx: Integer;                        // loops thru style sheets
  StyleSheet: IHTMLStyleSheet;              // reference to a style sheet
  RuleIdx: Integer;                         // loops thru style sheet rules
  Style: IHTMLRuleStyle;                    // ref to rule's style
begin
  if not Supports(Document, IHTMLDocument2, Doc) then
    Exit;
  StyleSheets := Doc.styleSheets;
  for SheetIdx := 0 to Pred(StyleSheets.length) do
  begin
    if Supports(StyleSheets.item(SheetIdx), IHTMLStyleSheet, StyleSheet) then
    begin
      for RuleIdx := 0 to Pred(StyleSheet.rules.length) do
      begin
        Style := StyleSheet.rules.item(RuleIdx).style;
        Style.backgroundImage := '';  // removes any background image
        Style.backgroundColor := '';  // resets background colour to default
      end;
    end;
  end;
end;