plz give me code for matching the two fields in two differcnt visualforce . so what i do

Here i given the SOQL code for update and that generating the compile error like field 'Chatter_Monitor_Policy_Keyword__c' can not be filtered in query call.

string abc=obj[0].Chatter_Monitor_Policy_Keyword__c;
string s ='%'+ abc + '%';
List<Chatter_Monitor_Policy__c> records = [SELECT Id, Chatter_Monitor_Policy_Keyword__c from Chatter_Monitor_Policy__c where Chatter_Monitor_Policy_Keyword__c Like:s and CreatedById =: UserInfo.getUserId()];
if(records.size()!=null)
        {
            for(Integer i=0;i<records.size();i++)
            {
                     records[0].Chatter_Monitor_Policy_Keyword__c = s;
                     update records[0];
            }
   

Hi all,

I have written a Visualforce PDF with extension class to call the list of contacts and a button on Button on Opportunity pagelayout .

The buttons works as if stagename == site visit it should give an error else open the PDF.

But here the problem is onclick javascript is working properly but im not getting the CONTACT values in visualforce page.

Visualforce page and Button is on Opportunity 

Javascript&colon;

var a = '{!Opportunity.StageName}'; 
if(a == 'Site Visit') 
alert('Please fill the Application Details');  
else 
window.open('/apex/Application_PDF?scontrolCaching=1&id={!Opportunity.Id}');

 Thanks in Advance...