It seems to be one common practice on websites which intend to give the user text for copying/pasting to place this text in an
<textarea/> and pre-select it for the user. However, these same websites often prevent the user from selecting the text manually by reverting the selection and blocking most mouse events whenever the user clicks on the element or tries to manually select it.
This is preventing me from copying/pasting this text. To copy in X11, one first selects text with the first mouse button. To paste, one uses the middle mouse button.
In my situation, since the browser implements its own sort of clipboard (with GTK+’s help?), I am able to use the context menu to copy the text from one part of the browser to another, such as the URI bar or page composer, and, once the text is in there, highlight it with the first mouse button and the paste it at the destination. However, this is an extra step and very annoying and limiting.