I've been using HomeSite for a very long time (since it belonged to Allaire); although I do not use it to it's fullest ability, I prefer it over Dreamweaver. Anyway, a fellow employee asked me a question today to which I never knew this existed. I have a file open. When the gutter is showing (whether the line numbers are on or off) and I click in the gutter next to a line of code, a little red "stop sign" icon appears and highlights the line of code in red. When I click it again, the line of code is highlighted in green and a green bar covers the middle of the stop sign. A third click removes the icon and the highlighted line of code. What is the function of this stop sign and highlighting?