Pseudo-selector :first-letter not working

Just as the title says, I am trying to use css
p:first-letter{text-transform: capitalize}

but it does not do anything. Can some one show me how do I achieve this. Thanks.

It’s supposed to be used with 2 colons. However, a single colon also works for me.

p::first-letter{text-transform: capitalize}

Example :

Thanks for your reply. It did not work for me still and I think it has to do with something else in my application css.