Its and it's belong to two different families.
One family has no apostrophes: his, hers, its.
The other family all has apostrophes: he's, she's, it's.
To check whether its has an apostrophe, substitute another member of the family:
This sort of error is hideously obvious in web content. Some readers (me included) always notice an its/it's error. Instant credibility crash as we subconsciously assume, 'Typo, ignorance, alarm bells, out of here!'
Some people half-learned a perfectly good old rule (an apostrophe replaces a missing letter). Unfortunately that half-knowing can torture the writer into dithering and questioning and delaying. If that's you, learn the family rule instead and start afresh.