How a salesforce program run?

I want to know how a salesforce progrma runs

for example:

   A java program run in Jvm and create class file .......

   like that how a salesforce program run to provide output.

i want to use jquery validation plugin in salesforce.


i name the id in salesforce but when it comes to html the id is changed.


exmp:

id="uname"

id="j_id0:login:uname"


pls help me to solve this problem i am not geting the out put

how to populate input fields when the lookup is selected?

I am doing a project. where i need to get values using lookup.

The object and the controller are custom. I want to take value to the visualforce page from controller.

I got this code from internet.

<apex:page controller="FileManager ">
    <apex:form >
            <apex:inputFile value="{!file}" />
        <apex:commandbutton action="{!go}" value="go"/>
    </apex:form>
</apex:page>

public class FileManager 
{
    public PageReference go() {
        return null;
    }


    public Blob file { get; set; }

    public PageReference submit() 
    {
        ContentVersion v = new ContentVersion();
        v.versionData = file;
        v.title = 'from VF';
        v.pathOnClient ='/foo.txt';
        insert v;
        return new PageReference('/' + v.id);
    }

}

I dont know how the code works? How can i know that location of the file which is uploaded?

Code for retrieving the uploaded file?

I am doing a project. where i need to get values using lookup.

The object and the controller are custom. I want to take value to the visualforce page from controller.

I got this code from internet.

<apex:page controller="FileManager ">
    <apex:form >
            <apex:inputFile value="{!file}" />
        <apex:commandbutton action="{!go}" value="go"/>
    </apex:form>
</apex:page>

public class FileManager 
{
    public PageReference go() {
        return null;
    }


    public Blob file { get; set; }

    public PageReference submit() 
    {
        ContentVersion v = new ContentVersion();
        v.versionData = file;
        v.title = 'from VF';
        v.pathOnClient ='/foo.txt';
        insert v;
        return new PageReference('/' + v.id);
    }

}

I dont know how the code works? How can i know that location of the file which is uploaded?

Code for retrieving the uploaded file?