onLoad is an event function in the browser's Document Object Model.
The timeline looks something like this;
* Browser sends HTTP Request to server.
* Server receives the Request and executes your ASP to prepare an HTTP Response.
* Server sends the Response to the browser.
* Browser pumps the Response into its Document Object Model, runs any inlinescript, runs any DOM events, and renders the page.
So chances are your ASP execution on the server has been over for a long while before the onLoad fires in the browser.. at least a long while in computing terms.