HTML website practice exercise
Okay, I am not sure exactly in what limits your exercise is, but I'll answer to what I think is good web standard. (I've been a web developer for ~4 years)


Don't use the align attribute. HTML is supposed to be a markup language. Use CSS to control the appearance of your html elements. In this case something like h1 { text-align: center; } should do just fine.
Don't use the &lt;br /&gt; tags for other things than actual line-breaks (that is, to break text). I would remove all &lt;br /&gt; tags, since you don't need them in this exercise. Elements like ul, li and p are by default block elements, which flows vertically. If you need more space between elements, use margin/padding instead. However, img is not a block element by default, so you can either wrap it in a div or make it a block element using CSS like img { display: block; }.
Do not put a ul inside a p tag. Close the p tag and then add another p tag after the ul instead.
Fine detail: insert line breaks in text to increase readability. A typical practice is to keep lines less than 80 characters.


Btw, you do know that there are validator tools for HTML, right?

EDIT: Full code, in a better way: (Note that I chose to preserve one br tag. Maybe it can be an exercise to figure out why)

&lt;!DOCTYPE HTML&gt;
&lt;html&gt;
    &lt;head&gt;
        &lt;style&gt;
            h1 { text-align: center; }
            img { display: block; }
        &lt;/style&gt;
        &lt;title&gt;BLA| Welcome &lt;/title&gt;
    &lt;/head&gt;
    &lt;body&gt;
            &lt;h1&gt;Meet Jack&lt;/h1&gt;
            &lt;img src="http://www.htmliseasy.com/exercises/jack.gif" alt="Meet Jack" /&gt;
            &lt;p&gt;He is Jack. He is an odd little boy that just got an empty box for his
               birthday. He may &lt;em&gt;look&lt;/em&gt; happy but is a &lt;em&gt;little&lt;/em&gt;
               disappointed. Now he will have to put a little things in the box.&lt;br /&gt;
               Jack would really like...&lt;/p&gt;
            &lt;ul&gt;
                &lt;li&gt;Roller blades&lt;/li&gt;
                &lt;li&gt;Magic tricks&lt;/li&gt;
                &lt;li&gt;Anything Pokemon&lt;/li&gt;
                &lt;li&gt;A motorized Lego set&lt;/li&gt;
            &lt;/ul&gt;
            &lt;p&gt;You can get all this (and more) at an online toy store. Two very popular
               ones are &lt;a href="http://www.toysrus.com/"&gt;toysrus.com&lt;/a&gt; and
               &lt;a href="http://www.etoys.com/"&gt;eToys&lt;/a&gt;.&lt;/p&gt;

    &lt;/body&gt;
&lt;/html&gt;