Onload Event Error

Good Day, I had an application that was working in production on rollbase.ph, we tested the application in rollbase.com to test the new version, we've encountered some bug in the onload event of the pages. Here's the scenario of the problem: 1,) In my page called "new coverage" during loading of the page i've created a script that will hide some sections upon load of the said page, but instead i've got an error "Uncaught TypeError: Cannot read property 'innerHTML' of null". This is from my script where the hiding process is executed. 2.) I've checked the script if there are syntax issues that caused the said error, but to no avail we didn't found any problems in the code and this exact script is working in rollbase.ph with the earlier version of rollbase. 3.) We tested to move the script component from the top page to the bottom page and after saving the error was fixed, I was wondering if this was the supposed behavior of the script component, i believe that location of the script component s