Salesforce Error 'You have uncommitted work pending. Please commit or rollback before calling out.'

Split transaction into two separate Ajax processes

The first process inserts the record and the second performs the callout and is able to update the newly inserted record.

TestWsCallout page

<apex:page controller="TestWsCallout" tabstyle="Account">
    <apex:form >
        <apex:actionFunction action="{!InsertRecord}" name="InsertRecord_JS" Rerender="statuses" status="Status1" oncomplete="CallWebService_JS();"/>
        <apex:actionFunction action="{!CallWebService}" name="CallWebService_JS" status="Status2" reRender="statuses, msg"/>
        <apex:outputPanel id="statuses">
            <apex:actionStatus id="Status1" startText="...Inserting Record Into DB..." />
            <apex:actionStatus id="Status2" startText="...Calling Web Service..." />
        </apex:outputPanel>
        <apex:outputPanel id="msg">
            <apex:pageMessages />
        </apex:outputPanel>
        <div><input name="DoAction" class="btn" type="button" value="Do Action" onclick="InsertRecord_JS();return false;"/></div>
    </apex:form>
</apex:page>

TestWsCallout Class

public class TestWsCallout{
    
    Account myAccount;
   
    public PageReference InsertRecord() {
        myAccount = new Account(name = 'Test Account');
        insert myAccount;
        // Calling a Web Service here would throw an exception
        return null;
    }
    
    public PageReference CallWebService() {
        
        // Execute a call to a Web Service
        HttpRequest req = new HttpRequest();
        req.setEndpoint('http://MyWebService12345678790.com?id=' + myAccount.Id);
        req.setMethod('GET');
        HttpResponse response = new Http().send(req);
        
        // Simulate an update
        myAccount.Name = 'Test Account 2';
        update myAccount;        
        ApexPages.addMessage(new ApexPages.Message(ApexPages.Severity.CONFIRM, 'WebService Called on New Account: ' + myAccount.Name));
        return null;
    }
}