removing css category charge add-on tradition server control

greetings!

i've combined tradition symbol category news following:

<span class="btnorange">
    <input type="submit" id="ctl00_maincontent_m_goback" value="back" name="ctl00$maincontent$m_goback"/>
</span>

however, renders instead (note antipathetic "class" charge quarrel tag):

<span class="btnorange">
    <input type="submit" class="btnorange" id="ctl00_maincontent_m_goback" value="back" name="ctl00$maincontent$m_goback"/>
</span>

my tradition symbol category looks this:

[toolboxdata(@"<{0}:mybutton runat=server></{0}:mybutton>")]
public category mybutton : button
{
    open overrule vacant renderbegintag(htmltextwriter writer)
    {
       writer.addattribute(htmltextwriterattribute.class, this.cssclass);   
       writer.renderbegintag("span");
       base.renderbegintag(writer);
    }

    open overrule vacant renderendtag(htmltextwriter writer)
    {
       writer.renderendtag();
       base.renderendtag(writer);
    }
}

since i wholly need set category charge camber tag, illusory consolidate "blank out" category charge quarrel tag?