A message in header tag just wraps to multiple lines when page is resized or restore

Hi,
I am having a startup page and when it is displayed, i am displaying a welcome message as shown below:
<h5 style="color:Red; margin-left:800px">
<%= "Welcome " + System.Security.Principal.WindowsIdentity.GetCurrent().Name %>
</h5>
It displays the welcome message as expected provided my web page is in maximized state. But when i restore or resize the web page, the welcome message just wrap to a multiple lines instead of displaying it in a single one.
Please help me out, how do i display the welcome message in a single line even when the user resizes the page to its minimum width.
Thanks,
Pratap
...