Modern browsers offer the ability to edit the HTML source of a page while viewing it; for instance, on Firefox, with
right click - inspect element - right click on the line highlighted in blue - edit as HTML, I can modify any text appearing in any web page.
What happens if I alter the text of a click-through license in this way before clicking "OK"? One could argue that this is equivalent to striking out a clause from a contract before signing it; however, the other party typically has no way to figure out that it has happened, because it is a modification that I make only on my web browser, and the text of the page is usually not sent back to the server together with the button click.
What would be the legal validity of this behaviour? Suppose, for instance, that I get a witness to confirm that I clicked "I agree" on a modified page and not on the original one. You may assume that all parties are in the US, for simplicity.