An issue I noticed recently is with using a style tag in a visualforce page. The issue occurs when a $Resource is referenced.
An example would be the following in a page:
<style> .testMinusStyle { color: #FFF; background: #1797C0 url({!URLFOR($Resource.jQuery1x,'jQueryPlugins/jqEasySlidePanel/images/minus.png')}) 6% 55% no-repeat; } </style>
First, if you just copy and paste the above into an existing visualforce page in Welkin Suite, some sort of auto-formatting is occuring so what you actually get in the editor after pasting is:
<style> .testMinusStyle { color: #FFF; background: #1797C0 url({!URLFOR($Resource.jQuery1x,'jQueryPlugins/jqEasySlidePanel/images/minus.png'); } ) 6% 55% no-repeat; } </style>
The autoformatting is adding a semi-colon and splitting it into two items.
I ran into this when I was copying an existing page into a new page and the new page would save because of the formatting adjusted to css like this.
If you manually type/fix it, the page will save, although the editior does underline it in green with a validation error.