Exception to the rule?

I discovered a dilemma in the grammatical usage of ‘a’ or ‘an’. Before the relatively new word, HTML (hypertext markup language), which; in certain circles is used as a word such as LAZER or RADAR. The dilemma is visual and auditory, my ear says, “I have an HTML document.” But my eye demands I use ‘a’ before H. My theory is the word usage of HTML is compounded by the happenstance of it reading like a series of numbers. What do you think?

[Tdol]

'An' comes before a vowel sound, not simply a vowel, which is why we say 'an html document' or 'an MA'. You'll see the opposite with letters beginning with a vowel which is pronounced as a consonant:
an egg\a European
an umbrella\a university

[Francois]

I think this is similar to 'a hoax', or even 'a university'; you need to use 'a' to avoid an awkward pronunciation eg. a U-turn instead of an U-turn (would sound like "a new turn").

FRC

[Francois]

I'm late again

FRC

[Tdol]

Simultaneous posting.