There are many ways to change text size. The oldest and easiest way is to use the <font> and heading tags.

<font> tag
This tag is used to change the font of the text. Fonts have many properties such as size, color, type, etc. Here we use font tag to change text size. Later on we would cover ohter other properties of the font tag.

Its syntax is:

<font size="n"> This is what you will see! </font>

where n could be any integer between and including -6 and 6. 'Six' is not acceptable. It has to be the numeric character '6'. The viewer would not see the opening or ending tags. He will only see whatever is enclosed in the tag. Following is a guide to the sizes.

<font size="+3"> +3is this big </font>
<font size="+2"> +2is this big </font>
<font size="+1"> +1is this big </font>
<font size=-1"> -1is this big </font>
<font size="-2"> -2is this big </font>
<font size="-3"> -3is this big </font>

Note: All browser do not support all font sizes. Most browsers support sizes from -1 to +4. It is recommended that you stay within this range.

Heading tag:
The heading tag is intended to be used for headings only. This one has six sizes, one through six. Its syntax is as follows:

<Hn>This is what you will see!</Hn>

where n is any integer between and including one and six. Just like font size, this tag also accepts only numerical characters. Now let's get an idea of the sizes of this tag.

<H4> This is H4 </H4>

<H3> This is H3 </H3>

<H2> This is H2 </H2>

<H1> This is H1 </H1>

So what is the difference between font size and heading. The difference is that you can't type anything else on the same line as a heading. For example I can only do this with font size. Heading tag cannot change the size of any word in the middle of a sentence.