Magento save new category taking too much time

Question

I want to create my menu for my site, i go to Catalog --> Manage Categories and do these steps:

1. In the Categories panel on the left, click the Add Subcategory button
2. Enter a Name for the subcategory
3. Scroll down to the bottom of the form, and set Is Active to “Yes.”
4. Set Include in Navigation Menu to “Yes.”
5. Assign a URL Key to the category.
6. click the Save Category button

But when i click save button, in a new tab load this url and this page is empty: " your-website-address/catalog_category/save/key/e105f5985ead9f17c56fd52d35c7ff6a/id/4/?isAjax=true "

and it seems like the url of page that i create new category:

" your-website-address/catalog_category/index/key/04702be81885aa95b2e6eaf8a28349af/ "

and saving category take too much time and if i don't refresh the page it doesn't to be done!

when i refresh the page the new category be added!!! How can i fix this problem? Thank you

EDIT:

I found that i have this problem just in firefox!!! Why?

Answer 1

This is because when you save category then it also run indexes.So if you have enabled flat category,then set the indexing mode "Category Flat Data" to manual and then save.

Answer 2

It's because mod_security rule id: 373763. This rule prevent the mini-iframe in the page but the category form need it so the error occur.

I'm using cPanel and got the same error, turn this rule off will instantly fix this problem.