Diagonal lines on After Effects timeline?

[saraj51210346]

I am pretty new to After Effects and was following along to a tutorial when I started tweaking the keyframes around.... and then these lines came up. Any idea what they mean, if they are an issue, and/or how to get rid of them? 

[Jose Panadero]

This is not a problem. These diagonal lines indicate that you have trimmed the in point of your layer adding more frames to the start.

[AndersOfTheMuseum]

I find these grey lines a bit offputting visually? Any way to reset the layer to remove these lines? I have removed all keyframes and all the layers are images (not video)? 

[OussK]

You can set the in point to zero and move the layer manually to the position you want

[Rick Gerard]

The UI has all kinds of clues to tell you what you have done to a layer. The hash marks indicate the original in point of a layer that is made with a solid, a shape layer, a Text layer. They can be useful. If you really want them to go away, move the CTI to the right of them, press Alt/Option + [ to set a new in point, then reposition the layer in the timeline by dragging and reposition all of the keyframes.

Be careful about the tutorials you watch. There are a great many recipes from enthusiasts that have poorly described workflows and in many cases, pretty lousy advice. The best place to get started quickly with AE is the User Guide.