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onkeypress="return this.value.length<200 || event.which ===8" onpaste="return this.value.length<200 " 

function enforceMaxLengthForMultilineTextbox(textBox, maxLength) {
    var numberOfLineBreaks = 0;
    var tmpTextBox = textBox;
    tmpTextBox.value = textBox.value.substr(0, maxLength);

    numberOfLineBreaks = ((tmpTextBox.value.match(/\n/g) || []).length);

    if ((textBox.value.length + numberOfLineBreaks) > maxLength) {
        textBox.value = tmpTextBox.value.substr(0, maxLength - numberOfLineBreaks);
    }
}