The following will tell you whether or not all of the text is selected within a text input in all major browsers.

Example: http://www.jsfiddle.net/9Q23E/

Code:

function isTextSelected(input) {

    if (typeof input.selectionStart == number) {

        return input.selectionStart == 0 && input.selectionEnd == input.value.length;

    } else if (typeof document.selection != undefined) {

        input.focus();

        return document.selection.createRange().text == input.value;

    }

}