I have created some seamless patterns in corelDRAW. However, the patterns are not ACTUALLY seamless as I can see a tiny white line between two square objects. Is there a way to get rid of that tiny hairline-like white line so that the pattern looks actually seamless?
No idea what application nor version you are using.
In general, the first thing to suspect is the pattern you made. Without a sample file, hard to guess. Here's a vector pattern on a yellow background.
If you are using a bitmap, then usually the pattern is not made to a whole pixel and anti-aliasing is turned on (when exported as an image) from CD. The pattern made from a non-whole pixel drawing will always display as you have shown.
MikeWe is correct it is related to anti-aliasing.The best option is to select all of the objects and apply object hinting, this will bring them together.Another option it to export with anti-aliasing off, it will also look ok on screen if you use normal view.