Contact information validation
basically just cleaned up some redundant brackets, tags, added a comment and modified existing comments, fixed indentations etc. Then i ran it through JSLint(http://www.jslint.com/), enjoy :)!

$(document).ready(function() {
    $('nav a[href^="#"]').bind('click.smoothscroll',function (e) {
        e.preventDefault();
        var target = this.hash,
        $target = $(target);
        $('html, body').stop().animate({
            'scrollTop': $target.offset().top
        }, 900, 'swing', function () {
            window.location.hash = target;
        });
    });
    $('a[href=#top]').click(function(){
        $('html, body').animate({scrollTop:0}, 'slow');
        return false;
    });
    $(function() {
        $("nav select").change(function() {
            window.location = $(this).find("option:selected").val();
        });
    });

    //place ID's of all required fields here.
    required = ["name", "email", "message"];
    //if using an ID other than #email or #error then replace it here
    email = $("#email");
    phone = $("#tel");
    errornotice = $("#error");
    //the text to show up within a field when it is incorrect
    emptyerror = "Required field.";
    emailerror = "Invalid email.";
    nameerror = "Name";
    phoneerror = "Phone";
    messageerror = "Message";
    onlynumber = "Invalid phone.";

    $("#contact").submit(function(){    
        //validate required fields
        for (i = 0; i &lt; required.length; i++) {
            var input = $('#' + required[i]);
            if (input.val() == "" || input.val() == emptyerror || input.val() == nameerror || input.val() == messageerror) {
                input.addClass("needsfilled");
                input.val(emptyerror);
                errornotice.fadeIn(750);
            } else {
                input.removeClass("needsfilled");
            }
        }
        //validate the e-mail.
        if (!/^([a-zA-Z0-9_\.\-])+\@(([a-zA-Z0-9\-])+\.)+([a-zA-Z0-9]{2,4})+$/.test(email.val())) {
            email.addClass("needsfilled");
            email.val(emailerror);
        }

        //validate phone
        if(phone.val() != phoneerror) {
            if (!/\(?([0-9]{3})\)?([ .-]?)([0-9]{3})\2([0-9]{4})/.test(phone.val())) {
                phone.addClass("needsfilled");
                phone.val(onlynumber);
            }
        }

        //if any inputs on the page have the class 'needsfilled' the form will not submit
        if ($(":input").hasClass("needsfilled")) {
            return false;
        } else {
            errornotice.hide();
            return true;
        }
    });

    //clears any fields in the form when the user clicks on them
    $(":input").focus(function(){       
       if ($(this).hasClass("needsfilled") ) {
            $(this).val("");
            $(this).removeClass("needsfilled");
       }
    });


    $(function(){
        $('input, textarea').each(function(){
            var txtval = $(this).val();
            $(this).focus(function(){
                $(this).val('')
            });
            $(this).blur(function(){
                if($(this).val() == ""){
                    $(this).val(txtval);
                }
            });
        });
    });
});