Getting Random white dotted line across screen

[musicman59]

It is random and is only across internet windows, not the entire screen.

looks like morse code, short and long lines.. just one line. it goes away on its own.

appears randomly.


iMac 10.4.11 roughly 3-4 years old.

Do I have pending monitor issues ???

 

[Giaguara]

Hi,

Does it only happen in browser windows, or all applications?
When does it typically happen? Randomly, when some app is on or when Mac is getting hotter in use or ..?
If you take a screenshot (command-apple-4 then space and mouse key down to capture window, command-apple-3 for whole screen) does the white lines show in it? If it does, can you show a screenshot?
When did it start to happen?