refresh shows different logo, sometimes a different background, what's the problem? sftp?

I'm trying to upload files to my client's Wordpress theme but the strangest things are happening. 1) When I update the css (a simple background-color change), upload, and hit refresh, the change doesn't show. 2) When I hit refresh on the site multiple times, sometimes a bigger sized logo shows and sometimes the background comes up tiled, and sometimes the background comes up not tiled. I'm transferring files through sftp (first time 开发者_运维百科doing this). Could that be the issue? How can I resolve this? I tried clearing the cache but no dice.

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Could be from several reasons

• there is a load balancer ( and the picture gets on one of the servers but not on the other )
• there is a cache problem ( try deleting the cached files from the browser )
• there is a wp cache plugin affecting this