<script language="JavaScript">  
<!--  
nN=navigator.appName  
function MouseUpHandler(e) {  
if (nN=='Netscape') {  
if (document.getSelection()){  
if(frames.length){ var i;  
for(i=0;i<length;i++){ sts=frames[i].document.getSelection();  
if(sts){ break; } } }  
else{ sts=document.getSelection(); }  
newstr=sts.replace(/\n+/g,' ');  
sts=newstr.replace(/\ +/g,' ');  
if(sts.length > 100){ var i; i=0; sts=sts.slice(0,100); i=sts.lastIndexOf(' ');  
if (i>0){ sts=sts.slice(0,i); } }  
document.form.text.value=sts; } }  
else if (nN=='Microsoft Internet Explorer') {  
if (document.selection.createRange()){  
var range = document.selection.createRange(); var sts = range.text; }  
if (sts){ sts=sts.replace(/\ +/g, " ");  
document.form.text.value=sts; } }  
return true; }  
if (window.Event)  
document.captureEvents(Event.MOUSEUP);  
document.onmouseup = MouseUpHandler;  
//-->  
</script>  

Форма:  

<form name="form">  
<input type="text" size="30" name="text">  
</form>