I can handle this one as it's happened to me a couple of times also. I suspect a misplaced keystroke deleted the icon from your dock. There are two ways that I know to correct this.
1. Go to "applications" and click on Safari. That will "open" the program and also place the Safari icon on your dock.
2. Go to "applications" and click highlight Safari. Then right click and select "make alias". Then drag the Safari Alias to the dock.
In either case, the right click on the icon in the dock and select "Keep in Dock".
I can handle this one as it's happened to me a couple of times also. I suspect a misplaced keystroke deleted the icon from your dock. There are two ways that I know to correct this.
1. Go to "applications" and click on Safari. That will "open" the program and also place the Safari icon on your dock.
2. Go to "applications" and click highlight Safari. Then right click and select "make alias". Then drag the Safari Alias to the dock.
In either case, the right click on the icon in the dock and select "Keep in Dock".