Why is my screen doing this ?

[Wild Retic]

Random black areas, but if I hit resync, it instantly goes away.

[Zeratul]

Mine does the same.

I don’t know how to fix it.

[Wil]

You set your display width larger than what the server sends. If you move faster than the server can keep up, there's no buffer of already-sent tiles so you miss them. Hence black.

1000x700 is a reasonably good compromise between large view window and rarely blacked tiles.