js关于字符串连接错误！跪求指导啊！
严重: Servlet.service() for servlet jsp threw exception
java.lang.NumberFormatException: For input string: ""+k+""
at java.lang.NumberFormatException.forInputString(Unknown Source)
at java.lang.Integer.parseInt(Unknown Source)
at java.lang.Integer.valueOf(Unknown Source)
at org.apache.jasper.compiler.JspUtil.coerceToInt(JspUtil.java:765)
at org.apache.jasper.compiler.Generator$GenerateVisitor.convertString(Generator.java:3131)
at org.apache.jasper.compiler.Generator$GenerateVisitor.evaluateAttribute(Generator.java:2946)
at org.apache.jasper.compiler.Generator$GenerateVisitor.generateSetters(Generator.java:3051)
at org.apache.jasper.compiler.Generator$GenerateVisitor.generateCustomStart(Generator.java:2231)
at org.apache.jasper.compiler.Generator$GenerateVisitor.visit(Generator.java:1746)
at org.apache.jasper.compiler.Node$CustomTag.accept(Node.java:1530)
at org.apache.jasper.compiler.Node$Nodes.visit(Node.java:2361)
at org.apache.jasper.compiler.Node$Visitor.visitBody(Node.java:2411)
at org.apache.jasper.compiler.Node$Visitor.visit(Node.java:2417)
at org.apache.jasper.compiler.Node$Root.accept(Node.java:495)
at org.apache.jasper.compiler.Node$Nodes.visit(Node.java:2361)
at org.apache.jasper.compiler.Generator.generate(Generator.java:3459)
at org.apache.jasper.compiler.Compiler.generateJava(Compiler.java:231)
at org.apache.jasper.compiler.Compiler.compile(Compiler.java:354)
at org.apache.jasper.compiler.Compiler.compile(Compiler.java:334)
at org.apache.jasper.compiler.Compiler.compile(Compiler.java:321)
at org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:592)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:328)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:313)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:260)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:293)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:859)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:602)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489)
at java.lang.Thread.run(Unknown Source)

<script type="text/javascript" language="javascript">
 var flag=0;
 var speed=5;
 var MyMar=null;
 var mousedown=false;
 var scroll=null;
 var i=1;
 Direction='Left';
 function out(){
flag=xold;
 }
 function over(){
 
 }
 var x=0, y=0, xold=0, yold=0, xdiff=0, ydiff=0;
 function FindXY(loc) {
//document.getElementById("demo2").innerHTML=document.getElementById("demo1").innerHTML;
//window.alert(document.getElementById("demo").scrollLeft);
//window.alert(document.getElementById("demo1").offsetWidth);
//window.alert(5*i);
 x = (document.lay