I have a parent and couple of items in that.
&
Please note: The original poster edited their question to exclude percent after I posted this answer.
Yes, you simply need to figure out the percent that each will use. In this case, 20%.
Also, you have some slight problems with your HTML (missing quote and width= instead of the correct width:).
- Item 1
- Item 2
- Item 3
- Item 4
Update:
While you can get away without defining pixels by using a percentage, there is no way with block elements to get away without defining any width value (and width values are only valid as a unit or a percentage).
Not that I'm suggesting you use tables, but table cells are the only elements in HTML that sort of behave like what you are asking for.