php - Submitting more than one html tag cause 404 Error in Codeigniter and Grocery Crud? -

i'm using grocery crud codeigniter change database columns,but have problem when use html tags, 404 not found error in firebug.

the following work:

but following doesn't work because have tried style :

when click on source in top left of wysiwyg editor , try type in html, works , not:

<p>this works</p> 

the following doesn't work (404 not found):

<p> <p>hello</p> not work </p> 

the following doesn't work (404 not found ):
<p></p>

the following works
<p>aaaa</p>

idea why 404 if put empty

tag works if put inside ?? in advance long can see, works 1 tag if use more 1 tag doesn't work :

<h1> single line work </h1> 

but if use more 1 html tag won't work, example following doesn't work ( 404 not found ?)

<h1>hello</h1> <h1>world</h1> 

though there little information given, have inserted html tags inside visual mode of editor or html mode ? try inserting in html mode , paste. think issue @ end related special characters.