how to mix links ( <a> tag ) and headings ( <h1> tag ) in web standard?

According to web standards you aren't allowed to put block elements into inline elements.

As h1 is a block element and a is an inline element the correct way is:

<h1><a href="#">This is a title</a></h1>

Here is a link so you can learn more: w3 Visual formatting model

However, there is an exception that in HTML5 it is valid to wrap block-level elements (like div, p or h*) in anchor tags. Wrapping block-level elements in inline elements other than anchors still goes against the standards.

HTML5 updates this subject: it is now OK to wrap block-level elements with A's, as stated under another question: https://stackoverflow.com/a/9782054/674965 and here: http://davidwalsh.name/html5-elements-links

a > h1 will cause difficulty in selecting text

Since both are completely valid in HTML5, it is better to use h1 > a

As far as I understand HTML5 does allow you to wrap block level elements in link tags. However, bugs may show up in older browsers. I encountered this with Firefox 3.6.18 and got moz-rs-heading="" inserted into my code. Thus my styles broke. If you care about a work around, you can then wrap the link tags in divs. The following provides a better explanation of why the additional code works http://oli.jp/2009/html5-block-level-links/