PNG Image With Transparency Renders With White Background In All Browsers?

Due to the site being built in ASP.NET, changing the button to be an linked image and using JavaScript on it then isn't an option.

However, on the developed ASP.NET site, this issue is also occurring. But I've managed to fix it in ASP.NET by doing the following:

When calling the button, I've typed this out to begin with:

<asp:Button ID="GoBtn" runat="server" CssClass="searchbutton" />

Adding the parameter "BackColor="Transparent" removes the white background from the button. So the tag now reads as:

<asp:Button ID="GoBtn" runat="server" CssClass="searchbutton" BackColor="Transparent" />

This removes the white background in ASP.NET. At a total loss to explain why the button has a white background on it. Although I have read that using a GIF could solve the problem, but I haven't had time to see if this is true or not.

EDIT (24/01/2010)

I found out how to fix this issue in the HTML document, by pure accident!

What you need to do, in the CSS you have to call the following:

background-color: transparent;
border: none;

This removes the grey/white background on the back of the button, and it also removes the border of the button.