Found many times in the error logs of my server:
my_folder_name/my_file_name/url(data:image/png;base64,iVBORw0KGgo
AAAANSUhEUgAAAEYAAAAOCAYAAACSJWqFAAAABGdBTUEAALGPC%2fxhBQAAAAlwSFlz
AAALEgAACxIB0t1%2b%2fAAAAAd0SU1FB9oGAhENK17O5ogAAAAZdEVYdENvbW1lbnQ
AQ3JlYXRlZCB3aXRoIEdJTVBXgQ4XAAAAGXRFWHRTb2Z0d2FyZQBQYWludC5ORVQgdj
MuNS44NzuAXQAAA99JREFUSMfdlmtMm1UYx%2fkOM1vmBck2EIyZOiLZJRLlMhaXhQS
jmRiHiVmi7gKpjshlBAiMhYG0C3UdinyYCUYMgm6MsYVLuV%2fLaArl1pYWGLQwJ6OIE
eKnn%2bcdZc4CS6vDyJ7kn%2feck5Nz3vPL%2f3nO8fDYIDFpnwsZvjPL2Ss38T9eTF
TmdzT0ahi9paUmJgKNvxejfl6M%2b3phFt8BX0%2b0vp4hHo97WO1zNJtvE5rdyLOJbX
jHVZBbpsZo1TPSUIY%2byIdxAWRMyCSk932CTj9PHsnmcRk%2f%2bgv1COGQ1N7zfwAz
tbBIrWGKoKwWfFJv8vSpBqIVlWiNOkaH2tBGBWPxW3KNwXcTOvFtE3pUYN4QqhPa4uhL
bct6HfaCUsmF%2fPwVPy%2bNOY%2fbFhZoH79DZH4nPkkd%2bCS0E5lbg2aoF4OuhcZ
DQbTt2kxL4Fbad26mS6RWk9%2bmv60RILciyXm%2fAIUYV1hxB9RpyTnrBsYBQALkDE
v1wJgUgz%2ffxXB3jqzKAQKSGtnxWRMJpVq6BnUoFbnEhu7lZOgrfPD%2bXg7HvYTsy
POogp9iJQDbPTlDcRmM5BpHKpWtZ4pIAFQOGPegrOGi44X11A9PoLXNUNAwgrLOIPpjp
J3JoOr6DVo1AlJ3D58X5PFCShjbFK%2bzK%2fXVVdxh4y9A7kORUsriALPFhfk8TC47Z
5UUWo6X4y8TlnaZ%2bEtqrvWZsPxqJ1ueR8XVq0zMLlCsn6dk8Hc6zb%2bQcz6HgPT9b
JWHrbqWBMJf7iaUB2pLkavzk5Q%2f%2bT1MboFxSqHl2PdpKYGycnbGlpJW0olRpFVC
SgrmyWkuaueZ%2fe0PrFN2SnR26scXkZ%2fPZ1tu%2bKpr3YciXwK0bmD%2bdZ1ZTiVH
bVkNzlvpPyD7Ss3Zsg6%2bb%2b1FP2lBdkrG6ISNIq0d48g0tW0mCppttEwskph8Gu%2
bs8DUL7X3XuAvnP4PiVGhVa9SZmn4LA5NGBkzl9Pcp6OlKISP9JDcqK%2flGgPm2eZxL
HdMoNPOUNunIPJPF9nMHVtxKS25xLr421%2bA4HFO37mDcuK7NM5NoWtPR1gQz1BDIoD
qQ8qJDvPfum3SIwlthWqB2bJHi2m4%2b%2fPgYkZ%2fE8ExmBK5cy86wNlQM3eqh48p%2
bTOog8dINwqjeTX%2fVPgrPHSQ5OZmcPAVfXPyS9IS3UaX6Ex0bwZPxoRvzsO6E6baZ7
usxDAkYw9XBGKpfw1gVTp86kbpujbit5LyY9g4HThwkP8mH6q%2bf4%2fBHkY8%2fGMu
MNcQ42sxAU5IAc5ThmqOY2nOwTA9zTbx%2b9yhP4K2IZnv2EaJk0ahSvKku3PGPwfwJA
W1Er1YzJJgAAAAASUVORK5CYII%3d)
Any idea what this should be?
[edited by: tedster at 1:37 am (utc) on Jan 9, 2012]
[edit reason] line breaks added to prevent side-scroll [/edit]