CodeBurner for Opera

Text-based search.	The main tool is a text-based search for HTML elements, HTML attributes, CSS properties, CSS selectors, and CSS at-rules. The search happens live as you type, so usually you'll only have to type one or two letters to get the results you want.
Detailed but succinct results.	Search results show in the center panel, and have information about browser compatibility, standards-compliance, and a brief summary of usage. There are also links to further information on the SitePoint Reference web site.
Practical code examples.	Code examples open in the right-hand panel, and are practical examples with summaries to show you how an element, attribute or property can be used.
DOM-based search.	Click the DOM tab in the left-hand panel and you can inspect the DOM of any page — as a springboard to looking up information on HTML elements and attributes.
CSS inspection.	Click the CSS tab to inspect the stylesheets associated with the DOM view page, from which you can get information about CSS properties, selectors and at-rules.
Search for a selected element and attributes.	If you double-click on an element then you can perform a selection search. This displays information about the specified element, along with all the attributes that are defined for it, plus any other attributes that are valid for it, and all the CSS properties and selectors that currently apply to it (that may be specified or inherited).