How to jump on a position specified by line and column?

M-x goto-line (M-g g or M-g M-g) gets you to the beginning of the target line. Then you can use C-u 8 right to move to the target column. Note that this puts you in column 8, because Emacs numbers columns from 0, except that the command line option +LINE:COLUMN numbers columns from 1.

If you want an Emacs command where you can type 2:9, here's some code you can paste in your .emacs that allows you to write it as an argument to goto-line. Note that the code is only minimally tested in Emacs 23.

(defadvice goto-line (around goto-column activate)
  "Allow a specification of LINE:COLUMN instead of just COLUMN.
Just :COLUMN moves to the specified column on the current line.
Just LINE: moves to the current column on the specified line.
LINE alone still moves to the beginning of the specified line (like LINE:0)."
  (if (symbolp line) (setq line (symbol-name line)))
  (let ((column (save-match-data
                  (if (and (stringp line)
                           (string-match "\\`\\([0-9]*\\):\\([0-9]*\\)\\'" line))
                      (prog1
                        (match-string 2 line)
                        (setq line (match-string 1 line)))
                    nil))))
    (if (stringp column)
        (setq column (if (= (length column) 0)
                         (current-column)
                       (string-to-int column))))
    (if (stringp line)
        (setq line (if (= (length line) 0)
                       (if buffer
                         (save-excursion
                           (set-buffer buffer)
                           (line-number-at-pos))
                         nil)
                     (string-to-int line))))
    (if line
        ad-do-it)
    (if column
        (let ((limit (- (save-excursion (forward-line 1) (point))
                        (point))))
          (when (< column limit)
            (beginning-of-line)
            (forward-char column))))))

For Emacs 24+ I wrote another version function, because Gilles function not working for me (don't know why).

(defun go-to-line-and-column-cond (lc-cond)
  "Allow a specification of LINE:COLUMN or LINE,COLUMN instead of just COLUMN.                                                                                                              
Just :COLUMN or ,COLUMN moves to the specified column on the current line.                                                                                                                  
LINE alone still moves to the beginning of the specified line (like LINE:0 or LINE,0).                                                                                                      
By Default I'm bind it to M-g M-l.                                                                                                                                                          
The default value of the COLUMN is decrement by -1                                                                                                                                          
because all compilers consider the number of COLUMN from 1 (just for copy-past)"
  (interactive "sLine:Column:: ")
  (let (line delim column max-lines)
    (setq max-lines (count-lines (point-min) (point-max)))
    (save-match-data
      (string-match "^\\([0-9]*\\)\\([,:]?\\)\\([0-9]*\\)$" lc-cond)
      (setq line (string-to-number (match-string 1 lc-cond)))
      (setq delim (match-string 2 lc-cond))
      (setq column (string-to-number (match-string 3 lc-cond)))
      (if (not (equal delim "")) (if (> column 0) (setq column (1- column))))
      (if (= 0 line) (setq line (line-number-at-pos)))
      (if (> line max-lines) (setq line max-lines))
      (goto-line line)
      (move-to-column column)
      (message "Marker set to line %d column %s" (line-number-at-pos) (current-column))
      )))

(global-set-key (kbd "M-g M-l") 'go-to-line-and-column-cond)