function isEnter(e){ //e is event object passed from function invocation
    var characterCode // literal character code will be stored in this variable
    if(e && e.which){ //if which property of event object is supported (NN4)
        e = e
        characterCode = e.which //character code is contained in NN4's which property
    }
    else{
        e = event
        characterCode = e.keyCode //character code is contained in IE's keyCode property
    }

    if(characterCode == 13){ //if generated character code is equal to ascii 13 (if enter key)
        return true
    }
    else{
        return false
    }
}

function getCharCode(e){ //e is event object passed from function invocation
    var characterCode // literal character code will be stored in this variable
    if(e && e.which){ //if which property of event object is supported (NN4)
        e = e
        characterCode = e.which //character code is contained in NN4's which property
    }
    else{
        e = event
        characterCode = e.keyCode //character code is contained in IE's keyCode property
    }

    return characterCode

}