Sometimes I see "¿Que es eso?" when watching Spanish films. Is it a missprint of "¿Qué es eso?" where they have forgotten the acute on the e or does it mean something else?
The words qué, cuál/es, quién/es, cómo, cuán, cuánto/a/os/as, cuándo, dónde y adónde are written with acute accent (tilde diacrítica) when used in an interrogative or exclamatory manner.
You can read this in RAE,
There is no difference in meaning but when you see any of those words in a question without the accent, it is wrong.
I'll be the contrarian here.
¿que es eso? is a valid Spanish construction and distinct from ¿qué es eso?
With the accent, the phrase means "What is that?" because qué is an interrogative pronoun. But without the accent, the phrase means something more akin to "You mean it's that?" The word que (no accent) is often used in spoken Spanish to start off phrases without entirely too much rhyme or reason except perhaps to give a stronger link to the previous statement (cf. pues), not unlike English's so.
For example, imagine someone has just described you a person, and someone comes walking around the corner and you think it's that person, but you're a bit incredulous. You'd say, ¿Que es él/ella? and your friend would respond sí/no. If you asked ¿qué es él/ella your friend would just say pues, un ser humano :-) You actually can hear the difference in speech. Without the accent, there are only two stressed syllables and more likely than not, only three syllables in total /'que'se.so/. With the accent, there are three stressed syllables and four total /'que'es'eso/
Now, that all being said, ¿qué es eso? is going to be vastly more common than ¿que es eso?, and so it's probably just a typo.
Should be "¿Qué es eso?", with an acute accent, as explained in DPD:
Qué: Palabra tónica, que debe escribirse con tilde a diferencia del pronombre relativo o de la conjunción que.