A quick test show that Chrome, Firefox and IE accepts dotted, long, class a, and long with auth in decimal, octal, and hex notation. Firefox also accepts long overflow.

Non of them accept Dotted overflow, Class B or Class C.

Decimal Dotted http://192.168.0.1/

Decimal Dotted Overflow http://448.424.256.257/

Decimal Long http://3232235521/

Decimal Long Overflow http://7527202817/

Decimal Class A http://192.11010049/

Decimal Class B http://49320.1/

Decimal Class C http://12625920.1/

Decimal Long with auth http://fake.site@3232235521/

Octal Dotted http://0300.0250.00.01/

Octal Dotted Overflow http://0700.0650.0400.0401/

Octal Long http://030052000001/

Octal Long Overflow http://070052000001/

Octal Class A http://0300.052000001/

Octal Class B http://0140250.01/

Octal Class C http://060124000.01/

Octal Long with auth http://fake.site@030052000001/

Hex Dotted http://0xc0.0xa8.0x0.0x1/

Hex Dotted Overflow http://0x1c0.0x1a8.0x100.0x101/

Hex Long http://0xc0a80001/

Hex Long Overflow http://0x1c0a80001/

Hex Class A http://0xc0.0xa80001/

Hex Class B http://0xc0a8.0x1/

Hex Class C http://0xc0a800.0x1/

Hex Long with auth http://fake.site@0xc0a80001/