I saw a Spellmaster comment on apostrophes in plurals i.e. CD's rather than CDs. This one confuses me, can't I use my apostrophe for the missing letters? I ain't having a go Spellmaster - I'm an apostrophe spotter myself but I've never known where to stand on plural abbreviations!
No, you shouldn't use apostrophes for plurals, whether they are abbreviations or not. The plural of CD is CDs. CD's is a possessive, as in "the CD's cover is blue". In the plural, the possessive would be "the CDs' covers are blue".
The only time one MIGHT use an apostrophe in simple, as opposed to possessive, plural situations is where NOT doing so could cause confusion. For example, I would write: How many i's are there in Mississippi?...rather than...How many is are there in Mississippi? The question, of course, refers to the frequency of occurrence of the letter 'i' in the word.