resigning?

Sorry I don't have Chinese input with my notebook.

I didn't keep good relationship with my department's head. She gave me a written warning for my so-called poor performance. They may terminate my employment at any time in the 90 days if my future performance cannot be at a satisfactory level at their discretion.

My question is: does that mean they may fire me in the future? Does my future employers may know that when they do the background check?

I am considering to quit this job now...any suggestion is really appreciated, thanks!