You didn't mention it was a LinkButton.
This is not a good solution.
There's a better way to do this.
The reason it's not a good solution is because when the HTML is generated it will look like this:
- <a href="someUrl" ><span class="button"> text for the link button </span></a>
This is not valid HTML. You cannot have a <span> within an <a>.
Therefore, I recommend you remove the Label from within your LinkButton to avoid problems in browsers. Set the style for the LinkButton instead.
Are you attempting to make a "gradient" on the link button?
-Frinny