Sometimes you're coding and you find yourself forgetting your context. For example, look at this situation:

The cursor is on line 52. Imagine you're coding there and you're puzzling on some problem for some time. Wouldn't it be handy to know, without scrolling up (and then back down again to where you were working), what the method signature looks like? And does the method begin two lines above the visible code or 10 lines? That information can now, in NetBeans iDE 7.3 (and already in the 7.3 Beta) very easily be ascertained, by putting the cursor on the closing brace of the code block:

As you can see, a new vertical line is shown parallel to the line numbers, connecting the end of the method with its start, as well as, at the top of the editor, the complete method signature, together with the number of the line on which it's found. Very handy. Same support is found for other file types, such as in JavaScript files.