Encounter an issue that prompt and error message -There was an error with this fields customized event. Field: Window Event: onload Error:syntax error

Hi experts,

I've encountered an issue when I tried to access an a CRM page with greyed out field.

Any expert out here who can help? Many thanks in advance.

"There was an error with this field's customized event"

Field: Window

Event : onLoad

Error: syntax error