Image Validation using Javascript with .Net

<script language="javascript" type="text/javascript">       //************************     //Width to resize large images to     var maxWidth=100;     //Height to resize large images to     var maxHeight=100;     //valid file Types.      var fileTypes=["bmp","gif","jpg","jpeg","doc","pdf"];      //the id of the preview image tag      var outImage="previewField";      //what to display when the image is not valid      var defaultPic="Images/myprofile.gif";          // *********     var globalPic;     function preview(what)     {        var source=what;        var ext=source.substring(source.lastIndexOf(".")+1,source.length).toLowerCase();        for(var i=0;i<fileTypes.length; i++)        if(fileTypes[i]==ext)        break;        globalPic=new Image();        if(i<fileTypes.length)        globalPic.src=defaultPic;        else{        alert("THAT IS NOT A VALID IMAGE\n Please load an image with an extension of one of the following :\n\n"+fileTypes.join(", "));        return false;        }        setTimeout=("applyChanges()",200);            }      function applyChanges()      {       var field=document.getElementById('ctl00$ContentPlaceHolder1$imgGridUser');       var x=parseInt(globalPic.width);       var y=parseInt(globalPic.height);           if(x>maxWidth)       {         y*=maxWidth/x;         x=maxWidth;             }       if(y<maxHeight)       {        x*=maxHeight/y;        y=maxHeight;             }      field.style.display=(x<1 || y<1)?"none":"";      field.src=globalPic.src;      field.width=x;      field.height=y;      }      function ValidateImageUpload()      {       var Img=document.getElementById('fleImageUpload');         if(Img.value=="")         {          alert('Select Image File');          Img.focus();          return false;         }          if(Img.value!="")          {           var blvalue=preview(Img.value);           return blvalue;         }         return true;            }     </script>