HTTP URLs can only be sent over the Internet using the ASCII character-set, which often contain characters outside the ASCII set. So these unsafe characters must be replaced with a% followed by two hexadecimal digits.
The following table shows the ASCII symbols of the characters and their replacements which can be used in the URL before passing it to the server:
| ASCII | Symbol | Replacement |
|---|---|---|
| < 32 | Encode with %xx where xx is the hexadecimal representation of the character. | |
| 32 | space | + or %20 |
| 33 | ! | %21 |
| 34 | " | %22 |
| 35 | # | %23 |
| 36 | $ | %24 |
| 37 | % | %25 |
| 38 | & | %26 |
| 39 | ‘ | %27 |
| 40 | ( | %28 |
| 41 | ) | %29 |
| 42 | * | * |
| 43 | + | %2B |
| 44 | , | %2C |
| 45 | - | - |
| 46 | . | . |
| 47 | / | %2F |
| 48 | 0 | 0 |
| 49 | 1 | 1 |
| 50 | 2 | 2 |
| 51 | 3 | 3 |
| 52 | 4 | 4 |
| 53 | 5 | 5 |
| 54 | 6 | 6 |
| 55 | 7 | 7 |
| 56 | 8 | 8 |
| 57 | 9 | 9 |
| 58 | : | %3A |
| 59 | ; | %3B |
| 60 | < | %3C |
| 61 | = | %3D |
| 62 | > | %3E |
| 63 | ? | %3F |
| 64 | @ | %40 |
| 65 | A | A |
| 66 | B | B |
| 67 | C | C |
| 68 | D | D |
| 69 | E | E |
| 70 | F | F |
| 71 | G | G |
| 72 | H | H |
| 73 | I | I |
| 74 | J | J |
| 75 | K | K |
| 76 | L | L |
| 77 | M | M |
| 78 | N | N |
| 79 | O | O |
| 80 | P | P |
| 81 | Q | Q |
| 82 | R | R |
| 83 | S | S |
| 84 | T | T |
| 85 | U | U |
| 86 | V | V |
| 87 | W | W |
| 88 | X | X |
| 89 | Y | Y |
| 90 | Z | Z |
| 91 | [ | %5B |
| 92 | \ | %5C |
| 93 | ] | %5D |
| 94 | ^ | %5E |
| 95 | _ | _ |
| 96 | ` | %60 |
| 97 | a | a |
| 98 | b | b |
| 99 | c | c |
| 100 | d | d |
| 101 | e | e |
| 102 | f | f |
| 103 | g | g |
| 104 | h | h |
| 105 | i | i |
| 106 | j | j |
| 107 | k | k |
| 108 | l | l |
| 109 | m | m |
| 110 | n | n |
| 111 | o | o |
| 112 | p | p |
| 113 | q | q |
| 114 | r | r |
| 115 | s | s |
| 116 | t | t |
| 117 | u | u |
| 118 | v | v |
| 119 | w | w |
| 120 | x | x |
| 121 | y | y |
| 122 | z | z |
| 123 | { | %7B |
| 124 | | | %7C |
| 125 | } | %7D |
| 126 | ~ | %7E |
| 127 | %7F | |
| > 127 | Encode with %xx where xx is the hexadecimal representation of the character. |
原文：http://www.cnblogs.com/hephec/p/4556950.html