How important is the headline?

I think it is critical!

I also think you can apply this to most forms of advertising, both on and offline.

What maybe classed as the headline in an offline advert could be called the title tag on a web page, <H1> tag, maybe a subject line in an email campaign or even a forum thread title, business listing title, PPC advert etc.

You always need a hook to draw people into your advert/website/content.

I'm a great believer in changing them as well, experiment and tweak until you are happy with the conversion rate.

I think the title is the one of the most important aspects to your page. It should contain a hook that your target visitor can identify with which will make them read the next line down which could be a sub headline or your intro.

They can leave at any point so like the post said above. Split testing and heatmap testing can work wonders. Split test 1 thing at a time and only make small changes then analyze and repeat until that part is golden then move onto another part.

Some software can heatmap test your page to see at which point the visitor leaves the page. This can be really useful to pinpoint any points in your copy that are making visitors lose interest - then split test tweaking this bit until it works better.

. . . But the title is what will more often than not keep them on the page and get them to start to read/scan your page

I think something like a question as the headline is the best way to get the audience to engage with your advertising and to grab them straight away - something rhetorical like "looking for a...?"

Yes headline is most essential part . I agree to you friend .

An astounding statistic is another good one - like "99 per cent of... users agre..."

I think Headline or title is the most important part of any topic because it contains the brief summary about the topic.

Headline is very important, however, in my opinion, the goal of headline is not really to sell your product/service but rather to induce curiousity/interest and encourage the prospect to keep reading your marketing message (instead of just walking away from it).

Another thing about headlines is that you need to keep testing them over and over again...

I agree with Denisklicic. The goal isn’t to sell something in the headline, rather to lure them in and strike their curiosity. Ask yourself if you would click on the headline if you saw it amongst others, even ask friends their opinion on it.

Headline, actually is not the most important but rather one of the most important parts of all advertisements. In my own opinion, it serves as the teaser of the products/services you advertise, it's like the the frontliner so it should really have to grab the attention of people, especially the ones you target.