How can I call a javascript function, that is in the aspx page, from the Page_Load method, in the code-behind?
If you just want to call a JavaScript function ( and do not need to pass something from code-behind, then use this...)
document.onload = function () { your-function(); };
window.onload = function () { your-function(); };
document.readyState = function () { your-function(); }
... depending on your specific requirements.
Hope this makes sense to you & answers your question.