I've just read John Grenham's blog about missing Census forms on the NAI site....http://johngrenham.com/irishroots/?p=127
What a revelation. Not all census forms hit the online search, but you can find them if you know the general area where the ancestors lived by manipulating the address/URL. Each form has a unique URL so by changing the URL you can move to another form.
I had long wondered why my great grandfather's household form didn't show up in the search, even though I knew the area where they had lived since the household was listed in the House and Building Return form. I realised from that form that households 1-10 in his village did not appear in the search. However, I was able to find the household form for my great grandfather by manipulating the URL in the address bar using John Grenham's invaluable method.
" In your browser address-bar, you’ll see something like “census.nationalarchives.ie/reels/nai002500860/”. Just add 1 to that number to go forward a frame and subtract 1 to go back."
John also lists major omissions from the online census - what a pity the Irish Times no longer publishes his articles, and that NAI didn't install a scroll feature on the census forms....