请看下面的html
<html>
    <body>
        <TABLE cellSpacing="0" cellPadding="0" width="100%" border="1" >
            <TBODY>
                <TR height="30">
                    <TD style="WIDTH: 12px"></TD>
                    <TD class="BigCaption" style="WIDTH: 150px">Web Domain :&nbsp;<SPAN class="WarningDescription">*</SPAN>
                    </TD>
                    <TD>
                        <SELECT id="DWT189WebDomain"/>
                    </TD>
                </TR>
                <TR>
                    <TD></TD>
                    <TD vAlign="top" colSpan="2">
                        asfdassdgsdgfsdgfsdgfsdfffffffffffffffffffffffffffffffffffffffffffffsdgfsdfgsdgsdgfsdgfsdgsdg
                    </TD>
                </TR>
            </TBODY>
        </TABLE>
    </body>
</html>

显示这个页面，含有Web Domain的TD的实际长度绝对大于150px的。因为受第二行的colSpan的属性影响了
<html>
    <body>
        <TABLE cellSpacing="0" cellPadding="0" width="100%" border="1" style="table-layout:fixed" >
            <TBODY>
                <TR height="30">
                    <TD style="WIDTH: 12px"></TD>
                    <TD class="BigCaption" style="WIDTH: 150px">Web Domain :&nbsp;<SPAN class="WarningDescription">*</SPAN>
                    </TD>
                    <TD>
                        <SELECT id="DWT189WebDomain"/>
                    </TD>
                </TR>
                <TR>
                    <TD></TD>
                    <TD vAlign="top" colSpan="2">
                        asfdassdgsdgfsdgfsdgfsdfffffffffffffffffffffffffffffffffffffffffffffsdgfsdfgsdgsdgfsdgfsdgs
                    </TD>
                </TR>
            </TBODY>
        </TABLE>
    </body>
</html>

这才是我要的效果！呵呵！