Sidebar categories and tags not showing up in Wordpress

I have added:

1. categories
2. posts in each category
3. tags for both posts
4. widgets from backend of tags and categories

Now the tabs of tags and categories are showing up while the categories and tags added are not showing up.

When I inspect it through firebug, it shows me:

<ul style="display:none"> .

But haven't applied any such class.

I need a little more information on your template. If you're inspecting it via firebug, can you get the page and line number of the that seems to be the issue? I would check the document on the editor on the backend of your wordpress site, and see if you can just leave the ul tag (because it's structural) and ditch the style altogether (just delete or outcomment the style) and see how that works. You could also fish for the code by say, setting the ul style="display: true" or something like that.

You could also try and check the display settings on all the widgets to see that they are set to display. If you can show more of the code from the actual page where you see the error it would help.