Changing font size

All the replies address changing the font size in HTML, isn't it possible to change the font side in Design mode?

the easiest way is to add a specific calss to this sentence... but first there are two contexts...

Context 1... you want to apply the font size to the all TAG

so lets say that you have you sentence that way (I use a P TAG, but it could be any TAG

<p>The sentence</p>

you create and add a class to this TAG that way

<p class="myclass">The sentence</p>

Context 2... you want to apply a different font size in the middle of a TAG and focus on some words only

so you will have to add a SPAN TAG containing the class, that way

<p>The <span class="myclass">sentence</span></p>

now, in both context, you have to declare the class in a CSS sheet, or the STYLE TAG in the header of the HTML document

problem wit this latter solution is that this CSS class will be available only in this document and not in your entire web site.

So let's go for instance in this limited solution

go in between the HEAD TAG in the top of your document and add the following code

<style>
    .myclass {
        font-size:36px;
    }
</style>