Systems and methods for dynamically modifying properties of content elements within information resources by client-side computing devices are provided herein. A computing device may receive an information resource. The information resource may include a content element and a content modification script. The content modification script may include a predefined trigger event and a change list for modifying the information resource. The computing device may detect an occurrence of a predefined trigger event on the information resource. The computing device may determine that the information resource satisfies a condition of the change list, responsive to detecting the occurrence of the predefined trigger event. The computing device may set a property of the content element, responsive to determining that the information resource satisfies the condition. The computing device may add a modification indicator to the content element to prevent modification while the information resource satisfies the condition of the change list.