Under California law, a party generally forfeits an appellate argument regarding the erroneous admission or exclusion of evidence unless a timely and specific objection was made at trial. This means trial counsel must object clearly and on the record every time the defense attempts to introduce or exclude evidence relevant to notice, causation, or damages, even when the objection seems unlikely to be sustained. An unpreserved objection cannot be resurrected on appeal, no matter how meritorious it may have been. The same principle applies to jury instructions. If counsel believes a particular CACI instruction governing dangerous condition, notice, or the reasonable time to act should be modified or supplemented, that request must be made explicitly and denied on the record before the issue can be raised on appeal.