Vi

From Liki

From this nice link [1]:

a

   enter insert mode, the characters typed in will be inserted after the current cursor position. If you specify a count, all the text that had been inserted will be repeated that many times. 

h

   move the cursor to the left one character position. 

i

   enter insert mode, the characters typed in will be inserted before the current cursor position. If you specify a count, all the text that had been inserted will be repeated that many times. 

j

   move the cursor down one line. 

k

   move the cursor up one line. 

l

   move the cursor to the right one character position. 

r

   replace one character under the cursor. Specify count to replace a number of characters 

u

   undo the last change to the file. Typing u again will re-do the change. 

x

   delete character under the cursor. Count specifies how many characters to delete. The characters will be deleted after the cursor.