The situation is this: is there a site that has a sprite with buttons and icons, is CSS that works with sprites.
The buttons have 2 States: the mouse is, mouse is not.
So, somehow, in 50% of cases, normal state (no mouse) button is not displayed, as if the sprite is not. It would seem that this may be due to the fact that the sprite does not have time to upload by the time of rendering the page, but no. After the update button did not appear, although when you hover works. And the hover state in the sprite is below (images are loaded from the top down...).
Another point. If chrome dev tools debajit css code, and move the position of the sprite on a pixel back and forth, it appears. Again, after refreshing the page disappears.
After cleaning the cache as luck, or something!.
Here is a piece of CSS
padding:9px 15px 0;
background:url(sprites/buttons-sprite.png) -9px -9px no-repeat;
margin:15px auto 0
background:url(sprites/buttons-sprite.png) -9px -47px no-repeat