img tag onload not validated

Hello validator's Specialist

Validating http://sensibilidad.org.ar/sensibilidad/blog/adshow.asp written
in iso-8859-1, HTML 4.01 Transitional

I'm receiving  For Line 100, Column 126: there is no attribute "ONLOAD".

><IMG onload="resize(this)"

Have checked on answers, reported as solved, but looks not. Pls help.

I'm webmaster of this site. Much appreciate your valuable service on W3C

Best Regards,

Pedro