Querybuilder filter by item id
args.queryBuilder.constantExpression.add('<%= ToCoveoFieldName("Name") %> <> "404"');
I have tried using Id and ItemId in the place of name, with no success.
To find which fields are available, you can look in the CES Admin Tool for your generated field set (Configuration > Fields > Field set for [SitecoreIndexName] - [MachineName]-[SitecoreInstanceName]) or in the Index Browser for the document you want to filter (Index > Index Browser).
In your case, you can use "id", "indexableitemid" or "_id" which are all indexed as ShortIDs (e.g.: 110d559fdea542ea9c1c8a5df7e70ef9).
args.queryBuilder.constantExpression.add('<%= ToCoveoFieldName("_id") %> <> "110d559fdea542ea9c1c8a5df7e70ef9"');