Safari “Inspect Element” editing

Hi, hope someone can help! We all have been into a webpage were the development was so fast, old or cheap that the page has a set length or height in its code that makes it difficult to view or work with this page making it so annoying. A long time ago I found a solution in Safari where you just activate the “Inspect element” tool and find the HTML code and manually edit it. With this you can add a height=“100%” and the window will go 100%. But this is only momentary if I reload/refresh the page code will go back to the old height=“640”. so I just do the editing again and again and again, I am tired of this, so my question is: Is there a way to modify this with a find/replace html in the active window code using AppleScript?