how to make sub-list?

Dear All

I know how to make an ordered or un-ordered list using <ol> or <ul>, such as:

<ol>
<li>Something</li>
<li>SomeOtherThing</li>
</ol>

However, if I want to make a list like following:

1. Something
1.1 Something_1
1.2 Something_2
2. SomeOtherThing
2.1 SomeOtherThing_1
2.2 SomeOtherThing_2

What html/css code should I use?

<ul>
<li>Something</li>
<li>
<ul>
<li>Something</li>
<li>Something</li>
<li>Something</li>
</ul>
</li>
<li>Somethingg</a>
<ul>
<li>Something</li>
</ul>
</li>
<li>Something</li>
</ul>

Thats 1 simple way to do it. :)

thank you for your help.
Unfortunately, your codes do not seem to work.

thank you for your help.
Unfortunately, your codes do not seem to work.

Well.. Its working for me, in FF, IE, Chrome.. I dont know what ur doing wrong, but its the right code. ;)

Well.. Its working for me, in FF, IE, Chrome.. I dont know what ur doing wrong, but its the right code. ;)

actually it's not, or at lewast not for what OP is asking... look at attached screen shot... he needs to use
<ol>
<li> one </li>
<ol>
<li> sub one one </li>
<li> sub one two </li>
</ol>
<li> two </li>
<ol>
<li> sub two one </li>
<li> sub two two </li>
</ol>
<li> three </li>
</ol>
to acheive what he wants... my code is before, your code is demo'd after

Oh, i misunderstood the request. I didnt think that the problem was Getting numbers instead of "dot's".

Thank you.

I apologize for not explaining my question clearly. What I EXACTLYwant to achieve is:

1. Title_1
1.1 Title_1-1
1.2 Title_1-2
1.3 Title_1-3

2. Title_2
2.1 Title_2-1
2.2 Title_2-2
2.3 Title_2-3

What html/css code can make them?