If you are on the Summer 14 release, this is documented behaviour. According to the release notes (bold is mine) :
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New Rich Text Editor for HTML Area Home Page Components
We replaced the rich text editor in HTML Area home page components with a new version that supports more markup but doesn’t allow HTML to be manually entered.
You'd use the new Visualforce Area Home Page Component:
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New Visualforce Area Home Page Component
The new Visualforce Area home page component lets you create home page components with custom markup, including JavaScript and CSS, which are now restricted from use in HTML Area home page components. Use Visualforce Area home page components to add dynamic content to your home page. For example, you can present content from partner apps, display charts in conjunction with the Analytics API, or add a canvas app to the home page. Visualforce Area home page components can be added to the narrow or the wide column of the home page layout, and the referenced Visualforce page can use a standard or custom controller. You can include JavaScript in your Visualforce page, but because the component is rendered in an iframe on the home page layout, the JavaScript can’t interact with the page that contains the component.
Actually i want to hide several fields from EDIT layout of the lead page.I tried using a vf page(making width=0% and height=0) in a section, and it is working in lead detail page but not on edit layout page.Is there any other approach as home page will not allow to interact with the lead page as per your discussion thread.
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New Rich Text Editor for HTML Area Home Page Components
We replaced the rich text editor in HTML Area home page components with a new version that supports more markup
but doesn’t allow HTML to be manually entered.
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Then how we can achieve entering html. I want to include a textbox with a button to provide custom search to the customer.
Thanks,
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New Visualforce Area Home Page Component
The new Visualforce Area home page component lets you create home page components with custom markup, including
JavaScript and CSS, which are now restricted from use in HTML Area home page components. Use Visualforce Area
home page components to add dynamic content to your home page. For example, you can present content from partner
apps, display charts in conjunction with the Analytics API, or add a canvas app to the home page.
Visualforce Area home page components can be added to the narrow or the wide column of the home page layout, and
the referenced Visualforce page can use a standard or custom controller. You can include JavaScript in your Visualforce
page, but because the component is rendered in an iframe on the home page layout, the JavaScript can’t interact with
the page that contains the component.
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I would like to remove the Default Button in the Approval History Related List "Submit for Approval" from Opportunity Layout.
This way with de home page :
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js" type="text/javascript"></script>
<script>
$j = jQuery.noConflict();
if(window.location.href.indexOf(".com/006") != -1) {
$j(document).ready(function() {
$j("input[name='piSubmit']").hide();
});
}
</script>
But, with limitation is not possible.
How i can resolved? Any ideia?