$(document).ready():-

JQuery’s document.ready() method gets called as soon as DOM is ready (means browser has parsed the HTML and built the DOM tree). It is cross browser compatible means behave equally on all browsers. If your web page has large images, it will not wait for loading of images completely. Hence it may called before pageLoad() method. We can have multiple document.ready() methods on a web page that will be called in coming sequence.

pageLoad():-

pageLoad() method gets called when images and all associated resources of the page have been fully loaded. Suppose your web page has large size images then until all the images are not fully loaded on the page, pageLoad() method will not called. pageLoad() method is not browser compatible. We can have only one pageLoad() method on a web page.

$(document).ready()

1. Best for onetime initialization.

2. Called as soon as DOM is ready; may called slightly before than pageLoad().

3. Cross browser compatible.

4. Unable to re-attach the functionality to elements/controls of the page affected by partial postbacks.

pageLoad()

1. Not best for onetime initialization if used with UpdatePanel.

2. Not Cross browser compatible.

3. Best to re-attach the functionality to elements/controls of the page affected by partial postbacks with UpdatePanel.