function limitlength(obj, length){
var maxlength=length
if (obj.value.length>maxlength)
obj.value=obj.value.substring(0, maxlength)
}

function checkForm() 
{ 
    var gname, gemail, gurl, gmessage; 
    with(window.document.guestform) 
    { 
        gname    = txtName; 
        gemail   = txtEmail; 
        gurl     = txtUrl; 
        gmessage = mtxMessage; 
    } 

    if(trim(gname.value) == '') 
    { 
        alert('Please write your name'); 
        gname.focus(); 
        return false; 
    } 
 
    else if(trim(gemail.value) != '' && !isEmail(trim(gemail.value))) 
    { 
        alert('Please give valid email or leave empty'); 
        gemail.focus(); 
        return false; 
    } 
    else if(trim(gmessage.value) == '') 
    { 
        alert('Please write your message'); 
        gmessage.focus(); 
        return false; 
    } 
    else 
    { 
        return true; 
    } 
} 

function trim(str) 
{ 
    return str.replace(/^\s+|\s+$/g,''); 
} 

function isEmail(str) 
{ 
    var regex = /^[-_.a-z0-9]+@(([-a-z0-9]+\.)+(ad|ae|aero|af|ag|ai|al|am|an|ao|aq|ar|arpa|as|at|au|aw|az|ba|bb|bd|be|bf|bg|bh|bi|biz|bj|bm|bn|bo|br|bs|bt|bv|bw|by|bz|ca|cc|cd|cf|cg|ch|ci|ck|cl|cm|cn|co|com|coop|cr|cs|cu|cv|cx|cy|cz|de|dj|dk|dm|do|dz|ec|edu|ee|eg|eh|er|es|et|eu|fi|fj|fk|fm|fo|fr|ga|gb|gd|ge|gf|gh|gi|gl|gm|gn|gov|gp|gq|gr|gs|gt|gu|gw|gy|hk|hm|hn|hr|ht|hu|id|ie|il|in|info|int|io|iq|ir|is|it|jm|jo|jp|ke|kg|kh|ki|km|kn|kp|kr|kw|ky|kz|la|lb|lc|li|lk|lr|ls|lt|lu|lv|ly|ma|mc|md|mg|mh|mil|mk|ml|mm|mn|mo|mp|mq|mr|ms|mt|mu|museum|mv|mw|mx|my|mz|na|name|nc|ne|net|nf|ng|ni|nl|no|np|nr|nt|nu|nz|om|org|pa|pe|pf|pg|ph|pk|pl|pm|pn|pr|pro|ps|pt|pw|py|qa|re|ro|ru|rw|sa|sb|sc|sd|se|sg|sh|si|sj|sk|sl|sm|sn|so|sr|st|su|sv|sy|sz|tc|td|tf|tg|th|tj|tk|tm|tn|to|tp|tr|tt|tv|tw|tz|ua|ug|uk|um|us|uy|uz|va|vc|ve|vg|vi|vn|vu|wf|ws|ye|yt|yu|za|zm|zw)|(([0-9][0-9]?|[0-1][0-9][0-9]|[2][0-4][0-9]|[2][5][0-5])\.){3}([0-9][0-9]?|[0-1][0-9][0-9]|[2][0-4][0-9]|[2][5][0-5]))$/i; 
    return regex.test(str); 
}