Pop-up message breaking CSS

Question

I am using the following C# to create a pop-up error message when data is not fully inputted and a button is pressed:

Page.ClientScript.RegisterStartupScript(typeof(Page), Guid.NewGuid().ToString(), "alert('Error Message')", true);

The pop-up is working, however, it appears to be breaking the CSS of the page.

Before:

After:

How do I fix this?

Answer 1

只需在javascript中而不是在ASP.net中创建按钮