Almost all HTML tags are combinable. For example, you can use italic AND underlined! together. However, there are some rules. For example, close tags in the order you use them. Looking at my example, since the tag is inside the tag, close the tag first. Also, as a general rule, <form> tags should sit outside of tables, like this:

<form action="post.asp" method="post">
	<table>
		<tr>
			<td>Name:</td><td><input type="text" name="firstName" /></td>
		</tr>
		<tr>
			<td>Submit:</td><td><input type="submit" value="Submit Me!" /></td>
		</tr>
	</table>
</form>

You are most likely to combine tags when linking an image. To do this, you would put your <a> tag around an image. The image also has a border="" attribute, which you can set to a width for an outline showing that it is a link, or set it to 0 so that it does not show a link border.

(with border="2")

(with border="0")