How can i display error message on visualforce page  and i have code i.e for searching name,phone and email in leads .if name already exist then it will populate appropirate name,email and phone ,if suppose name its not there so i want to display info message.Here i have code but i am not getting error message so kindly let me know the solution ASAP. 

Controller:

public class theController {

   String searchText;
   List<Lead> results;

   public String getSearchText() {
      return searchText;
   }

   public void setSearchText(String s) {
      searchText = s;
   System.debug('SEARCHTEXT:'+searcHText);
   }

   public List<Lead> getResults() {
     
     if(results == null)
      {
       ApexPages.Message myMsg = new ApexPages.Message(ApexPages.Severity.FATAL, 'my error msg');
      }
   return results;
   }

   public PageReference doSearch() {
    
     results = (List<Lead>)[FIND :searchText RETURNING Lead(Name, Email, Phone)][0];
           
      return null;
   }
}

Page:

<apex:page controller="theController">
<apex:messages />
   <apex:form >
      <apex:pageBlock mode="edit" id="block">
         <apex:pageBlockSection >
            <apex:pageBlockSectionItem >
               <apex:outputLabel for="searchText">Search Text</apex:outputLabel>
               <apex:panelGroup >
                  <apex:inputText id="searchText" value="{!searchText}"/>
                  <apex:commandButton value="Go!" action="{!doSearch}"
                                      rerender="block" status="status"/>
               </apex:panelGroup>
            </apex:pageBlockSectionItem>
        </apex:pageBlockSection>
        <apex:actionStatus id="status" startText="requesting..."/>
        <apex:pageBlockSection title="Results" id="results" columns="1">
           <apex:pageBlockTable value="{!results}" var="l"
                               rendered="{!NOT(ISNULL(results))}">
              <apex:column value="{!l.name}"/>
              <apex:column value="{!l.email}"/>
              <apex:column value="{!l.phone}"/>
           </apex:pageBlockTable>
        </apex:pageBlockSection>
      </apex:pageBlock>
   </apex:form>
</apex:page>

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Reards

Rakheeb

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HI guys , whenever user is created it will generete email i.e username and new password to a perticular user.same thing i am doing on Contact  when the record is created  then i want to generate email to perticular contact person i.e username and new password.So how can i do that kindly let me know solution.

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I have followed everything as per the above link, after that when i goto the sites /apex/MyHomePage it gives me the following error in the site:

"Sorry for the inconvenience. We'll be back shortly. Please email us if you need to get in touch."

and through email i received the following error information:

Apex script unhandled exception by user/organization: 005A0000001KhMN/00DA00000009MmR

Visualforce Page: /apex/sitelogin

caused by: System.NullPointerException: Attempt to de-reference a null object

Class.FBCAuthenticator.value: line 35, column 45
External entry point

Debug Log:
20.0 APEX_CODE,DEBUG;APEX_PROFILING,INFO;CALLOUT,INFO;DB,INFO;SYSTEM,DEBUG;VALIDATION,INFO;VISUALFORCE,INFO;WORKFLOW,INFO

Kindly help in resolving this issue.