missing closing div tag

I have a website which is composed of Master page and a ascx that fits into it. Unfortenatly I see the page doesn't look the way I expect it to.

After a short investigation I figured out it can be a missing closing div tag in my ascx. The problem is that the code is very very long.

Is there any automated开发者_开发知识库 online tool that can show me places in code that can lead to this? Meaning places with missing div tag?

any other creative idea would be helpful as well

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You can use W3C validator: http://validator.w3.org/ or you can install (if you are using Firefox) https://addons.mozilla.org/en-US/firefox/addon/html-validator/