Yes, these are elementary spelling words, but cruise the web and you will see them misspelled all over the place.
- forty the error is to try to make it match four
- ninety the mistake is leaving out the e
- February the error is in omitting the first r
- Wednesday the error is in omitting the first d
NOTE: This peculiar spelling incorporates an old noun possessive. The day of the week was named for the god Woden. Before English started using apostrophe s to indicate the possessive of a noun, it used a genitive ending –es. Wednesday is literally Woden’s Day. Somewhere along the way the o in Woden became an e.
Speaking of days and months, another frequently misspelled word in this category is calendar. The error is writing er for ar.