Created attachment 8898996 [details] tdtest.html User Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:55.0) Gecko/20100101 Firefox/55.0 Build ID: 20170814072924 Steps to reproduce: See the simple attached HTML file, which has two table cells, and a flash script in the second table cell which contains a button. Load the page; confirm hovering over the button works. Open developer tools, and add a display:none rule to the first td. Attempt to hover over the button. Change tabs, then change back to this tab. Attempt to hover over the button. Resize the window. Attempt to hover over the button. Actual results: After adding display:none, the hoverable area is now 100px too far right; the width of the td you hid (if you hover over the left side of the button, nothing happens; but you can hover too far right). After changing tabs, and changing back, the entire button is unhoverable. After resizing the window, the button becomes hoverable again. The hover area continues to fail each time you switch tabs. Expected results: It appears some width calculations are not being correctly calculated when a td is hidden. Note that this is not directly related to this flash script only; the actual problem is occurring for me on a much larger website, but I grabbed the above as the simplest swf file I could file online to confirm it happened with other flash files too, rather than being specific to one. This also isn't specific to developer tools; for example, in my original website, I was using AdBlockPlus to hide a specific td on the page.
PS - given the potential insecurity of flash, if anyone is uncomfortable with using the one provided, feel free to substitute with any flash app of your choice that contains buttons etc. The above was the first one that popped up in Google (and for narrowing things down I removed the whole script embed and used a simple object).