Have used speckie Speckie - Spell Check Internet Explorer
now for a couple of years and just lately found the dictionaries Speckie - Spell Check Internet Explorer
but it hs increasingly become problematical as in not applying the zig zag line under the wrong spelling and forgetting the add t dictionary feature.
Now have found a part solution > go to Tools in IE9 > click on Speckie settings and you can tick the third box down and change th e colour of the zig zag as in my pic and then Apply.
The change will not take place until the next window you open. It does not remove the problem altogether but at lest alleviates it a little.
There are times when the zig zag disappears that you can click outside the post box and they re appear but not always.